Open in new tab Feature . MBCI-FTD...

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Feature	MBCI-FTD criterion definition
	Important that each of these features represents a change from previous functioning
Apathy without moderate-severe dysphoria	Apathy is defined as a lack of interest in or indifference towards usual or previously rewarding activities (e.g. the patient may no longer be interested in hobbies), reduced interest in the activities of others, a loss of motivation, a lack of spontaneity, decreased initiation of activities or social interactions (e.g. the patient may require prompting to finish a task, does not begin or sustain conversations with family or friends), social withdrawal, a loss of drive. This criterion should not be considered present if the patient reports moderate-severe dysphoria (per self-report or self-completed questionnaire, such as the Geriatric Depression Scale or the Beck Depression Inventory). We strongly caution against using caregiver or informant reports of depression here, because a lack of motivation may be interpreted by family members as depressed mood.
Behavioural disinhibition	Behavioural disinhibition may occur in or out of the social context, and may manifest as: impulsive, rash or careless actions (e.g. extreme spending, gambling, reckless driving, stealing, sharing confidential information such as a credit card number, talking to strangers as though they are friends, touching strangers), socially inappropriate behaviour (e.g. using inappropriate coarse or rude language, inappropriate laughing, offensive jokes, sexually-explicit or hurtful comments), a loss of manners or decorum (e.g. cutting in line, belching, picking teeth), or a disregard for personal hygiene (e.g. wearing stained clothing). Behavioural disinhibition applies even if one understands and regrets an action. Note that if the patient is displaying excessive joviality, this should not be counted under disinhibition but rather as its own feature.
Irritability/agitation	Irritable or agitated patients tend to be overreactive, labile, impatient, or ‘cranky’. They may be resistant to help and hard to handle at times, and may shout at family members or others, or even hit or kick. Patients experiencing irritability or agitation may have difficulty coping with delays or waiting for planned activities. Caregivers might describe labile patients as being ‘quick to anger’ or ‘flying off the handle’. Mild irritability that does not represent a significant decline or change in behaviour should not be included here. This is distinct from pseudobulbar affect, which is not part of this criterion.
Repetitive behaviours (simple and complex)	Repetitive behaviours may be simple or complex in nature. Simple perseverative behaviours might include: tapping, pacing, fidgeting, wrapping string, handling buttons or other small objects, rubbing, clapping, humming, rocking, lip pursing, lip smacking, picking or scratching, throat clearing. Complex perseverative behaviours include compulsive and/or ritualistic behaviours. Examples include: collecting objects, hoarding, counting, cleaning rituals, walking fixed routes, lining up objects in a particular order, checking.
Joviality/gregariousness	Patients who display joviality or gregariousness may be described as being more jocular, outgoing, friendly, or jolly than usual. The patient may act excessively happy or be overly sociable, and may appear to ‘feel too good’.
Appetite changes/hyperorality	In the MBCI-FTD criteria, appetite changes may be present in either direction [hyperphagia (overeating), or hypophagia (undereating)], as per the Neuropsychiatric Inventory. However, based on clinical experience, we highlight that hyperphagia is the more common appetite change in prodromal bvFTD, and it is rare for a prodromal bvFTD patient to be hypophagic, unless there is concomitant amyotrophic lateral sclerosis (ALS). Appetite changes may manifest as an increased preference for certain types of food, particularly sweet foods or carbohydrates, or may display rigid food preferences. Patients may engage in binge eating, and in some cases gain significant amounts of weight. (Note, however, that in cases of ALS weight loss may be observed.). Patients may increase their consumption of alcohol or cigarettes. Hyperorality, or the tendency to want to put objects in the mouth, may also be observed.
Reduced empathy or sympathy	Reduced empathy or sympathy is defined as a reduced ability to read others’ emotional cues or understand another’s point of view. It may manifest as a diminished responsiveness to others’ feelings or needs, or a lack or personal warmth. Patients may appear indifferent to the feelings of others, or display a lack of regard for others’ distress (affective empathy). The ability to take the perspective of others is an important aspect of empathy (cognitive empathy), and therefore patients who have difficulty ‘seeing things from someone else’s point of view’ are considered to have poor empathy. Reduced social engagement is also a common presentation of reduced empathy, though care should be taken to ensure that this is not simply due to apathy (a lack of motivation to engage). Caregivers may report that the patient who lacks empathy is ‘emotionally distant’. In terms of gathering this information in a clinical context, we strongly suggest that reduced empathy or sympathy is ascertained from clinical interview with a caregiver or informant. Questionnaires (such as the Interpersonal Reactivity Index Empathic Concern or Perspective Taking subscale) may be used for informant report, but we highlight that scores should be interpreted against appropriate normative data.
Reduced insight	Reduced insight can be ascertained by a discrepancy between the reports of caregivers or informants and patients themselves. The patient may exhibit poor insight for cognitive changes, behavioural changes, or both. Patients with motor symptoms (e.g. from ALS) may deny or minimize these symptoms. A lack of insight into any behavioural or cognitive change is enough for this feature to be present. Importantly, the clinician should make a judgement on the reliability of the informant; if the informant has very little contact with the patient, or if it appears they may be overestimating symptoms because of their own mental state (e.g. high stress or anxiety over diagnosis), their report may be given less weight. If no informant is available, clinicians should be careful in marking this criterion as present.
Neuropsychological profile	The neuropsychological profile of MBCI-FTD is defined as a clinical impairment on executive function tests (e.g. set-shifting, letter fluency, cognitive inhibition, abstract reasoning, planning, etc.) or naming tests, in the context of intact or relatively preserved time/place orientation and visuospatial skills. If there is an impairment or relative weakness in orientation or visuospatial functioning, this criterion is not met. We acknowledge that although in the MBCI-FTD criteria a clinical impairment on at least one test is required (demographically-adjusted z-score ≤ −1.5), clinically significant relative impairments, especially if observed across multiple tests within the same domain, should not be discounted. Likewise, change from previous cognitive functioning or from estimated prior functioning should be considered. However, this judgment should only be made by trained clinical neuropsychologists. We also caution against using screening tests, such as the Mini-Mental State Examination, as the sole tool to determine the neuropsychological profile of the patient. Finally, given the pervasiveness of executive dysfunction, and its tendency to affect performance in other cognitive domains (e.g. complex figure drawing, memory testing), we strongly advise that this criterion be applied based on the judgment of a clinical neuropsychologist, and not subject or informant complaints.
Poor social cognition	The ‘poor social cognition’ criterion should only be applied if there is meaningfully reduced performance on a validated measure of social cognition. In developing the MBCI-FTD criteria, we examined only two aspects of social cognition: understanding of social expectations and socioemotional sensitivity. Reduced understanding of social expectations refers to a lack of ‘social semantic knowledge’, or a lack of knowledge of the contexts in which certain behaviours are appropriate, and specifically refers to a tendency to break social rules. For example, indicating that it is acceptable to laugh when someone else trips and falls. The endorsement of breaking multiple social norms is particularly specific to FTD. In the current study we have used the Social Norms Questionnaire, but note that this instrument is highly specific to North American culture and is not necessarily suitable for use outside North America unless it is adapted. Poor socioemotional sensitivity refers to a sensitivity and responsiveness to subtle emotional expressions during face-to-face interactions, for example having the ability to control how one comes across to others depending on the impression they want to give. Socioemotional sensitivity can be measured with the Revised Self-Monitoring Scale. We highlight that it is likely that there are other aspects of social cognition (e.g. theory of mind) that will prove to be useful for this criterion, and we strongly recommend that future studies consider using other social cognition tools in the context of the MBCI-FTD criteria. This criterion will benefit from future refinement, and we intend for this criterion to encompass impairments on social cognition tasks beyond the two tests we had access to in the current study Caution is recommended when assessing social cognition, as this ability varies widely in the general population; therefore, special care must be taken to ensure that this represents a change from previous functioning.

Feature	MBCI-FTD criterion definition
	Important that each of these features represents a change from previous functioning
Apathy without moderate-severe dysphoria	Apathy is defined as a lack of interest in or indifference towards usual or previously rewarding activities (e.g. the patient may no longer be interested in hobbies), reduced interest in the activities of others, a loss of motivation, a lack of spontaneity, decreased initiation of activities or social interactions (e.g. the patient may require prompting to finish a task, does not begin or sustain conversations with family or friends), social withdrawal, a loss of drive. This criterion should not be considered present if the patient reports moderate-severe dysphoria (per self-report or self-completed questionnaire, such as the Geriatric Depression Scale or the Beck Depression Inventory). We strongly caution against using caregiver or informant reports of depression here, because a lack of motivation may be interpreted by family members as depressed mood.
Behavioural disinhibition	Behavioural disinhibition may occur in or out of the social context, and may manifest as: impulsive, rash or careless actions (e.g. extreme spending, gambling, reckless driving, stealing, sharing confidential information such as a credit card number, talking to strangers as though they are friends, touching strangers), socially inappropriate behaviour (e.g. using inappropriate coarse or rude language, inappropriate laughing, offensive jokes, sexually-explicit or hurtful comments), a loss of manners or decorum (e.g. cutting in line, belching, picking teeth), or a disregard for personal hygiene (e.g. wearing stained clothing). Behavioural disinhibition applies even if one understands and regrets an action. Note that if the patient is displaying excessive joviality, this should not be counted under disinhibition but rather as its own feature.
Irritability/agitation	Irritable or agitated patients tend to be overreactive, labile, impatient, or ‘cranky’. They may be resistant to help and hard to handle at times, and may shout at family members or others, or even hit or kick. Patients experiencing irritability or agitation may have difficulty coping with delays or waiting for planned activities. Caregivers might describe labile patients as being ‘quick to anger’ or ‘flying off the handle’. Mild irritability that does not represent a significant decline or change in behaviour should not be included here. This is distinct from pseudobulbar affect, which is not part of this criterion.
Repetitive behaviours (simple and complex)	Repetitive behaviours may be simple or complex in nature. Simple perseverative behaviours might include: tapping, pacing, fidgeting, wrapping string, handling buttons or other small objects, rubbing, clapping, humming, rocking, lip pursing, lip smacking, picking or scratching, throat clearing. Complex perseverative behaviours include compulsive and/or ritualistic behaviours. Examples include: collecting objects, hoarding, counting, cleaning rituals, walking fixed routes, lining up objects in a particular order, checking.
Joviality/gregariousness	Patients who display joviality or gregariousness may be described as being more jocular, outgoing, friendly, or jolly than usual. The patient may act excessively happy or be overly sociable, and may appear to ‘feel too good’.
Appetite changes/hyperorality	In the MBCI-FTD criteria, appetite changes may be present in either direction [hyperphagia (overeating), or hypophagia (undereating)], as per the Neuropsychiatric Inventory. However, based on clinical experience, we highlight that hyperphagia is the more common appetite change in prodromal bvFTD, and it is rare for a prodromal bvFTD patient to be hypophagic, unless there is concomitant amyotrophic lateral sclerosis (ALS). Appetite changes may manifest as an increased preference for certain types of food, particularly sweet foods or carbohydrates, or may display rigid food preferences. Patients may engage in binge eating, and in some cases gain significant amounts of weight. (Note, however, that in cases of ALS weight loss may be observed.). Patients may increase their consumption of alcohol or cigarettes. Hyperorality, or the tendency to want to put objects in the mouth, may also be observed.
Reduced empathy or sympathy	Reduced empathy or sympathy is defined as a reduced ability to read others’ emotional cues or understand another’s point of view. It may manifest as a diminished responsiveness to others’ feelings or needs, or a lack or personal warmth. Patients may appear indifferent to the feelings of others, or display a lack of regard for others’ distress (affective empathy). The ability to take the perspective of others is an important aspect of empathy (cognitive empathy), and therefore patients who have difficulty ‘seeing things from someone else’s point of view’ are considered to have poor empathy. Reduced social engagement is also a common presentation of reduced empathy, though care should be taken to ensure that this is not simply due to apathy (a lack of motivation to engage). Caregivers may report that the patient who lacks empathy is ‘emotionally distant’. In terms of gathering this information in a clinical context, we strongly suggest that reduced empathy or sympathy is ascertained from clinical interview with a caregiver or informant. Questionnaires (such as the Interpersonal Reactivity Index Empathic Concern or Perspective Taking subscale) may be used for informant report, but we highlight that scores should be interpreted against appropriate normative data.
Reduced insight	Reduced insight can be ascertained by a discrepancy between the reports of caregivers or informants and patients themselves. The patient may exhibit poor insight for cognitive changes, behavioural changes, or both. Patients with motor symptoms (e.g. from ALS) may deny or minimize these symptoms. A lack of insight into any behavioural or cognitive change is enough for this feature to be present. Importantly, the clinician should make a judgement on the reliability of the informant; if the informant has very little contact with the patient, or if it appears they may be overestimating symptoms because of their own mental state (e.g. high stress or anxiety over diagnosis), their report may be given less weight. If no informant is available, clinicians should be careful in marking this criterion as present.
Neuropsychological profile	The neuropsychological profile of MBCI-FTD is defined as a clinical impairment on executive function tests (e.g. set-shifting, letter fluency, cognitive inhibition, abstract reasoning, planning, etc.) or naming tests, in the context of intact or relatively preserved time/place orientation and visuospatial skills. If there is an impairment or relative weakness in orientation or visuospatial functioning, this criterion is not met. We acknowledge that although in the MBCI-FTD criteria a clinical impairment on at least one test is required (demographically-adjusted z-score ≤ −1.5), clinically significant relative impairments, especially if observed across multiple tests within the same domain, should not be discounted. Likewise, change from previous cognitive functioning or from estimated prior functioning should be considered. However, this judgment should only be made by trained clinical neuropsychologists. We also caution against using screening tests, such as the Mini-Mental State Examination, as the sole tool to determine the neuropsychological profile of the patient. Finally, given the pervasiveness of executive dysfunction, and its tendency to affect performance in other cognitive domains (e.g. complex figure drawing, memory testing), we strongly advise that this criterion be applied based on the judgment of a clinical neuropsychologist, and not subject or informant complaints.
Poor social cognition	The ‘poor social cognition’ criterion should only be applied if there is meaningfully reduced performance on a validated measure of social cognition. In developing the MBCI-FTD criteria, we examined only two aspects of social cognition: understanding of social expectations and socioemotional sensitivity. Reduced understanding of social expectations refers to a lack of ‘social semantic knowledge’, or a lack of knowledge of the contexts in which certain behaviours are appropriate, and specifically refers to a tendency to break social rules. For example, indicating that it is acceptable to laugh when someone else trips and falls. The endorsement of breaking multiple social norms is particularly specific to FTD. In the current study we have used the Social Norms Questionnaire, but note that this instrument is highly specific to North American culture and is not necessarily suitable for use outside North America unless it is adapted. Poor socioemotional sensitivity refers to a sensitivity and responsiveness to subtle emotional expressions during face-to-face interactions, for example having the ability to control how one comes across to others depending on the impression they want to give. Socioemotional sensitivity can be measured with the Revised Self-Monitoring Scale. We highlight that it is likely that there are other aspects of social cognition (e.g. theory of mind) that will prove to be useful for this criterion, and we strongly recommend that future studies consider using other social cognition tools in the context of the MBCI-FTD criteria. This criterion will benefit from future refinement, and we intend for this criterion to encompass impairments on social cognition tasks beyond the two tests we had access to in the current study Caution is recommended when assessing social cognition, as this ability varies widely in the general population; therefore, special care must be taken to ensure that this represents a change from previous functioning.

The presence of behavioural/neuropsychiatric features can be ascertained by clinical interview and with questionnaires, such as the Neuropsychiatric Inventory,⁸⁶ the Frontal Behavioral Inventory,⁸⁷ the Frontal Systems Behavior Scale,⁸⁸ or the Cambridge Behavioural Inventory.⁸⁹

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Feature	MBCI-FTD criterion definition
	Important that each of these features represents a change from previous functioning
Apathy without moderate-severe dysphoria	Apathy is defined as a lack of interest in or indifference towards usual or previously rewarding activities (e.g. the patient may no longer be interested in hobbies), reduced interest in the activities of others, a loss of motivation, a lack of spontaneity, decreased initiation of activities or social interactions (e.g. the patient may require prompting to finish a task, does not begin or sustain conversations with family or friends), social withdrawal, a loss of drive. This criterion should not be considered present if the patient reports moderate-severe dysphoria (per self-report or self-completed questionnaire, such as the Geriatric Depression Scale or the Beck Depression Inventory). We strongly caution against using caregiver or informant reports of depression here, because a lack of motivation may be interpreted by family members as depressed mood.
Behavioural disinhibition	Behavioural disinhibition may occur in or out of the social context, and may manifest as: impulsive, rash or careless actions (e.g. extreme spending, gambling, reckless driving, stealing, sharing confidential information such as a credit card number, talking to strangers as though they are friends, touching strangers), socially inappropriate behaviour (e.g. using inappropriate coarse or rude language, inappropriate laughing, offensive jokes, sexually-explicit or hurtful comments), a loss of manners or decorum (e.g. cutting in line, belching, picking teeth), or a disregard for personal hygiene (e.g. wearing stained clothing). Behavioural disinhibition applies even if one understands and regrets an action. Note that if the patient is displaying excessive joviality, this should not be counted under disinhibition but rather as its own feature.
Irritability/agitation	Irritable or agitated patients tend to be overreactive, labile, impatient, or ‘cranky’. They may be resistant to help and hard to handle at times, and may shout at family members or others, or even hit or kick. Patients experiencing irritability or agitation may have difficulty coping with delays or waiting for planned activities. Caregivers might describe labile patients as being ‘quick to anger’ or ‘flying off the handle’. Mild irritability that does not represent a significant decline or change in behaviour should not be included here. This is distinct from pseudobulbar affect, which is not part of this criterion.
Repetitive behaviours (simple and complex)	Repetitive behaviours may be simple or complex in nature. Simple perseverative behaviours might include: tapping, pacing, fidgeting, wrapping string, handling buttons or other small objects, rubbing, clapping, humming, rocking, lip pursing, lip smacking, picking or scratching, throat clearing. Complex perseverative behaviours include compulsive and/or ritualistic behaviours. Examples include: collecting objects, hoarding, counting, cleaning rituals, walking fixed routes, lining up objects in a particular order, checking.
Joviality/gregariousness	Patients who display joviality or gregariousness may be described as being more jocular, outgoing, friendly, or jolly than usual. The patient may act excessively happy or be overly sociable, and may appear to ‘feel too good’.
Appetite changes/hyperorality	In the MBCI-FTD criteria, appetite changes may be present in either direction [hyperphagia (overeating), or hypophagia (undereating)], as per the Neuropsychiatric Inventory. However, based on clinical experience, we highlight that hyperphagia is the more common appetite change in prodromal bvFTD, and it is rare for a prodromal bvFTD patient to be hypophagic, unless there is concomitant amyotrophic lateral sclerosis (ALS). Appetite changes may manifest as an increased preference for certain types of food, particularly sweet foods or carbohydrates, or may display rigid food preferences. Patients may engage in binge eating, and in some cases gain significant amounts of weight. (Note, however, that in cases of ALS weight loss may be observed.). Patients may increase their consumption of alcohol or cigarettes. Hyperorality, or the tendency to want to put objects in the mouth, may also be observed.
Reduced empathy or sympathy	Reduced empathy or sympathy is defined as a reduced ability to read others’ emotional cues or understand another’s point of view. It may manifest as a diminished responsiveness to others’ feelings or needs, or a lack or personal warmth. Patients may appear indifferent to the feelings of others, or display a lack of regard for others’ distress (affective empathy). The ability to take the perspective of others is an important aspect of empathy (cognitive empathy), and therefore patients who have difficulty ‘seeing things from someone else’s point of view’ are considered to have poor empathy. Reduced social engagement is also a common presentation of reduced empathy, though care should be taken to ensure that this is not simply due to apathy (a lack of motivation to engage). Caregivers may report that the patient who lacks empathy is ‘emotionally distant’. In terms of gathering this information in a clinical context, we strongly suggest that reduced empathy or sympathy is ascertained from clinical interview with a caregiver or informant. Questionnaires (such as the Interpersonal Reactivity Index Empathic Concern or Perspective Taking subscale) may be used for informant report, but we highlight that scores should be interpreted against appropriate normative data.
Reduced insight	Reduced insight can be ascertained by a discrepancy between the reports of caregivers or informants and patients themselves. The patient may exhibit poor insight for cognitive changes, behavioural changes, or both. Patients with motor symptoms (e.g. from ALS) may deny or minimize these symptoms. A lack of insight into any behavioural or cognitive change is enough for this feature to be present. Importantly, the clinician should make a judgement on the reliability of the informant; if the informant has very little contact with the patient, or if it appears they may be overestimating symptoms because of their own mental state (e.g. high stress or anxiety over diagnosis), their report may be given less weight. If no informant is available, clinicians should be careful in marking this criterion as present.
Neuropsychological profile	The neuropsychological profile of MBCI-FTD is defined as a clinical impairment on executive function tests (e.g. set-shifting, letter fluency, cognitive inhibition, abstract reasoning, planning, etc.) or naming tests, in the context of intact or relatively preserved time/place orientation and visuospatial skills. If there is an impairment or relative weakness in orientation or visuospatial functioning, this criterion is not met. We acknowledge that although in the MBCI-FTD criteria a clinical impairment on at least one test is required (demographically-adjusted z-score ≤ −1.5), clinically significant relative impairments, especially if observed across multiple tests within the same domain, should not be discounted. Likewise, change from previous cognitive functioning or from estimated prior functioning should be considered. However, this judgment should only be made by trained clinical neuropsychologists. We also caution against using screening tests, such as the Mini-Mental State Examination, as the sole tool to determine the neuropsychological profile of the patient. Finally, given the pervasiveness of executive dysfunction, and its tendency to affect performance in other cognitive domains (e.g. complex figure drawing, memory testing), we strongly advise that this criterion be applied based on the judgment of a clinical neuropsychologist, and not subject or informant complaints.
Poor social cognition	The ‘poor social cognition’ criterion should only be applied if there is meaningfully reduced performance on a validated measure of social cognition. In developing the MBCI-FTD criteria, we examined only two aspects of social cognition: understanding of social expectations and socioemotional sensitivity. Reduced understanding of social expectations refers to a lack of ‘social semantic knowledge’, or a lack of knowledge of the contexts in which certain behaviours are appropriate, and specifically refers to a tendency to break social rules. For example, indicating that it is acceptable to laugh when someone else trips and falls. The endorsement of breaking multiple social norms is particularly specific to FTD. In the current study we have used the Social Norms Questionnaire, but note that this instrument is highly specific to North American culture and is not necessarily suitable for use outside North America unless it is adapted. Poor socioemotional sensitivity refers to a sensitivity and responsiveness to subtle emotional expressions during face-to-face interactions, for example having the ability to control how one comes across to others depending on the impression they want to give. Socioemotional sensitivity can be measured with the Revised Self-Monitoring Scale. We highlight that it is likely that there are other aspects of social cognition (e.g. theory of mind) that will prove to be useful for this criterion, and we strongly recommend that future studies consider using other social cognition tools in the context of the MBCI-FTD criteria. This criterion will benefit from future refinement, and we intend for this criterion to encompass impairments on social cognition tasks beyond the two tests we had access to in the current study Caution is recommended when assessing social cognition, as this ability varies widely in the general population; therefore, special care must be taken to ensure that this represents a change from previous functioning.

Feature	MBCI-FTD criterion definition
	Important that each of these features represents a change from previous functioning
Apathy without moderate-severe dysphoria	Apathy is defined as a lack of interest in or indifference towards usual or previously rewarding activities (e.g. the patient may no longer be interested in hobbies), reduced interest in the activities of others, a loss of motivation, a lack of spontaneity, decreased initiation of activities or social interactions (e.g. the patient may require prompting to finish a task, does not begin or sustain conversations with family or friends), social withdrawal, a loss of drive. This criterion should not be considered present if the patient reports moderate-severe dysphoria (per self-report or self-completed questionnaire, such as the Geriatric Depression Scale or the Beck Depression Inventory). We strongly caution against using caregiver or informant reports of depression here, because a lack of motivation may be interpreted by family members as depressed mood.
Behavioural disinhibition	Behavioural disinhibition may occur in or out of the social context, and may manifest as: impulsive, rash or careless actions (e.g. extreme spending, gambling, reckless driving, stealing, sharing confidential information such as a credit card number, talking to strangers as though they are friends, touching strangers), socially inappropriate behaviour (e.g. using inappropriate coarse or rude language, inappropriate laughing, offensive jokes, sexually-explicit or hurtful comments), a loss of manners or decorum (e.g. cutting in line, belching, picking teeth), or a disregard for personal hygiene (e.g. wearing stained clothing). Behavioural disinhibition applies even if one understands and regrets an action. Note that if the patient is displaying excessive joviality, this should not be counted under disinhibition but rather as its own feature.
Irritability/agitation	Irritable or agitated patients tend to be overreactive, labile, impatient, or ‘cranky’. They may be resistant to help and hard to handle at times, and may shout at family members or others, or even hit or kick. Patients experiencing irritability or agitation may have difficulty coping with delays or waiting for planned activities. Caregivers might describe labile patients as being ‘quick to anger’ or ‘flying off the handle’. Mild irritability that does not represent a significant decline or change in behaviour should not be included here. This is distinct from pseudobulbar affect, which is not part of this criterion.
Repetitive behaviours (simple and complex)	Repetitive behaviours may be simple or complex in nature. Simple perseverative behaviours might include: tapping, pacing, fidgeting, wrapping string, handling buttons or other small objects, rubbing, clapping, humming, rocking, lip pursing, lip smacking, picking or scratching, throat clearing. Complex perseverative behaviours include compulsive and/or ritualistic behaviours. Examples include: collecting objects, hoarding, counting, cleaning rituals, walking fixed routes, lining up objects in a particular order, checking.
Joviality/gregariousness	Patients who display joviality or gregariousness may be described as being more jocular, outgoing, friendly, or jolly than usual. The patient may act excessively happy or be overly sociable, and may appear to ‘feel too good’.
Appetite changes/hyperorality	In the MBCI-FTD criteria, appetite changes may be present in either direction [hyperphagia (overeating), or hypophagia (undereating)], as per the Neuropsychiatric Inventory. However, based on clinical experience, we highlight that hyperphagia is the more common appetite change in prodromal bvFTD, and it is rare for a prodromal bvFTD patient to be hypophagic, unless there is concomitant amyotrophic lateral sclerosis (ALS). Appetite changes may manifest as an increased preference for certain types of food, particularly sweet foods or carbohydrates, or may display rigid food preferences. Patients may engage in binge eating, and in some cases gain significant amounts of weight. (Note, however, that in cases of ALS weight loss may be observed.). Patients may increase their consumption of alcohol or cigarettes. Hyperorality, or the tendency to want to put objects in the mouth, may also be observed.
Reduced empathy or sympathy	Reduced empathy or sympathy is defined as a reduced ability to read others’ emotional cues or understand another’s point of view. It may manifest as a diminished responsiveness to others’ feelings or needs, or a lack or personal warmth. Patients may appear indifferent to the feelings of others, or display a lack of regard for others’ distress (affective empathy). The ability to take the perspective of others is an important aspect of empathy (cognitive empathy), and therefore patients who have difficulty ‘seeing things from someone else’s point of view’ are considered to have poor empathy. Reduced social engagement is also a common presentation of reduced empathy, though care should be taken to ensure that this is not simply due to apathy (a lack of motivation to engage). Caregivers may report that the patient who lacks empathy is ‘emotionally distant’. In terms of gathering this information in a clinical context, we strongly suggest that reduced empathy or sympathy is ascertained from clinical interview with a caregiver or informant. Questionnaires (such as the Interpersonal Reactivity Index Empathic Concern or Perspective Taking subscale) may be used for informant report, but we highlight that scores should be interpreted against appropriate normative data.
Reduced insight	Reduced insight can be ascertained by a discrepancy between the reports of caregivers or informants and patients themselves. The patient may exhibit poor insight for cognitive changes, behavioural changes, or both. Patients with motor symptoms (e.g. from ALS) may deny or minimize these symptoms. A lack of insight into any behavioural or cognitive change is enough for this feature to be present. Importantly, the clinician should make a judgement on the reliability of the informant; if the informant has very little contact with the patient, or if it appears they may be overestimating symptoms because of their own mental state (e.g. high stress or anxiety over diagnosis), their report may be given less weight. If no informant is available, clinicians should be careful in marking this criterion as present.
Neuropsychological profile	The neuropsychological profile of MBCI-FTD is defined as a clinical impairment on executive function tests (e.g. set-shifting, letter fluency, cognitive inhibition, abstract reasoning, planning, etc.) or naming tests, in the context of intact or relatively preserved time/place orientation and visuospatial skills. If there is an impairment or relative weakness in orientation or visuospatial functioning, this criterion is not met. We acknowledge that although in the MBCI-FTD criteria a clinical impairment on at least one test is required (demographically-adjusted z-score ≤ −1.5), clinically significant relative impairments, especially if observed across multiple tests within the same domain, should not be discounted. Likewise, change from previous cognitive functioning or from estimated prior functioning should be considered. However, this judgment should only be made by trained clinical neuropsychologists. We also caution against using screening tests, such as the Mini-Mental State Examination, as the sole tool to determine the neuropsychological profile of the patient. Finally, given the pervasiveness of executive dysfunction, and its tendency to affect performance in other cognitive domains (e.g. complex figure drawing, memory testing), we strongly advise that this criterion be applied based on the judgment of a clinical neuropsychologist, and not subject or informant complaints.
Poor social cognition	The ‘poor social cognition’ criterion should only be applied if there is meaningfully reduced performance on a validated measure of social cognition. In developing the MBCI-FTD criteria, we examined only two aspects of social cognition: understanding of social expectations and socioemotional sensitivity. Reduced understanding of social expectations refers to a lack of ‘social semantic knowledge’, or a lack of knowledge of the contexts in which certain behaviours are appropriate, and specifically refers to a tendency to break social rules. For example, indicating that it is acceptable to laugh when someone else trips and falls. The endorsement of breaking multiple social norms is particularly specific to FTD. In the current study we have used the Social Norms Questionnaire, but note that this instrument is highly specific to North American culture and is not necessarily suitable for use outside North America unless it is adapted. Poor socioemotional sensitivity refers to a sensitivity and responsiveness to subtle emotional expressions during face-to-face interactions, for example having the ability to control how one comes across to others depending on the impression they want to give. Socioemotional sensitivity can be measured with the Revised Self-Monitoring Scale. We highlight that it is likely that there are other aspects of social cognition (e.g. theory of mind) that will prove to be useful for this criterion, and we strongly recommend that future studies consider using other social cognition tools in the context of the MBCI-FTD criteria. This criterion will benefit from future refinement, and we intend for this criterion to encompass impairments on social cognition tasks beyond the two tests we had access to in the current study Caution is recommended when assessing social cognition, as this ability varies widely in the general population; therefore, special care must be taken to ensure that this represents a change from previous functioning.

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