A Case of Functional Movement Disorder Preceding Right Temporal Predominant Frontotemporal Degeneration

Frontotemporal degeneration (FTD) encompasses syndromes characterized by behavioral, cognitive, language, or motor impairments.1 Right temporal predominant variant FTD (rtvFTD), or behavioral-semantic variant,2 remains understudied. Early symptoms typically affect behavior and social cognition, but functional movements are rarely the first complaint.2 We present a patient who experienced hyperkinetic movements and balance and gait difficulties consistent with functional movement disorder for 4 years prior to typical right temporal FTD symptom onset. We present an 82-year-old right-handed woman. Aside from a daughter with multiple sclerosis, she has no family history of neurological or psychiatric disease. Before symptom onset, the patient was social, easygoing, and religious. In her late 70s, she suddenly started “walking like a drunken sailor.” Gradually, she developed abnormal, arrhythmic, truncal flexion-extension movements, present when standing, walking, and often when sitting, but absent when lying down (Video 1). These truncal jerks were variable in amplitude and direction, easily distractible, and context-dependent, including markedly improved or absent when dancing or listening to music, or walking with minimal support. Simultaneously, bifrontal headaches, exhaustion, myalgia, bowel and urinary issues, dysphagia, and dysarthria were reported. Extensive work-up, including head CT, returned normal. Trials of clonazepam, gabapentin, and sertraline provided no noticeable improvement, and she was referred to a movement disorders specialist. By the visit, the patient had developed behavioral and cognitive impairments, prompting a frontal gait disorder diagnosis and referral to cognitive neurology. Disinhibition, impulsivity, memory trouble, anomia, prosopagnosia, and functional decline were apparent. On exam, she was pleasant, alert, and mostly command-following, but disoriented to time and place. Cranial nerve, motor, and reflex testing were normal. However, her gait had a normal base, was slow, shuffling, and punctuated by distractible and arrhythmic truncal movements (Video 2). As she walked, she tried to find points of support without falling, even when they were far away from her. Her postural sway improved when she walked with the support of the wall (Video 3). Cognitive testing revealed deficits in language comprehension (Table 1). Head MRI demonstrated significant right > left anterior temporal lobe atrophy (Fig. 1). The patient fit criteria for probable FTD, rtvFTD subtype. Genetic testing was negative. Severely impaired per MMSE scoring. Intersecting pentagons were oddly drawn, with a square and little semicircles along one side. The following sentence was written in legible cursive: “Thank you, lord, for your SUN today, please Mary, help me with my Alzheimer's situation.” Most deficits were due to comprehension difficulties. Semantic fluency: −2.85 SD Phonemic Fluency: −1.79 SD Delayed recall: 0 Recognition testing: 2/3 shapes and 2/3 words correctly identified, with one false-positive shape recognition Given that her truncal movements and gait instability began almost 4 years before the cognitive and behavioral symptoms consistent of rtvFTD, and were characterized by a combination of positive signs of inconsistency and incongruence, including context dependence, resolution with distraction, absence of movements in the supine position, and improvement of gait with music and minimal tactile support, we concluded that the patient initially manifested a functional movement disorder preceding her eventual diagnosis of rtvFTD. Two years later, symptom progression was apparent. The patient stopped dancing, had two falls, required walking support, and her gait showed Parkinsonian features. RtvFTD, previously grouped with behavioral variant FTD or semantic variant primary progressive aphasia, is now recognized to most frequently present with disinhibition, altered empathy, memory deficits, and prosopagnosia. Language comprehension problems are common due to contralateral temporal lobe atrophy.2 Similar to our patient, somatic complaints without clear underlying cause have been reported recently and are increasingly recognized in rtvFTD, often with somatic delusional beliefs.3 Although functional movement disorder can precede Parkinson's disease,4 functional neurological disorder (FND) is rarely described as the first complaint in FTD. FTD can present with hyperkinetic or hypokinetic movements, commonly motor and vocal stereotypies or atypical parkinsonism, respectively.5, 6 There has only been one report of motor impairments occurring first: frontal gait syndrome presenting two years before behavioral and cognitive symptoms.7 However, unlike our patient, the prior reported patient had primarily frontal atrophy.7 Studies of rtvFTD have focused on behavioral and cognitive features, possibly overlooking potential movement and gait abnormalities.2, 3 Given our patient's motor features (consisting of inconsistency and incongruency: context dependent, resolved with distraction, absent in the supine position, and improved gait with minimal tactile support) and somatic complaints preceding behavioral and cognitive symptoms, motor FND was initially diagnosed, though later confounded by changes attributable to right temporal lobe atrophy. Her case represents the first report, to our knowledge, of a motor FND arising in the context of progressive anterior right temporal atrophy. This is particularly intriguing given the recent recognition of somatic symptoms in rtvFTD.3 Right temporal lobe dysfunction may also be related to motor impairments through its reciprocal connections with the basal ganglia, thalamus, and frontal cortices, role in attention and the integration of vestibular and spatial information, and participation in emotional regulation and sense of agency.8-10 Another proposed model is abnormal feedback processing in the right insula, which may lead to initiation of abnormal motor movements in attempt to correct or compensate for those predictions or signals.6 To our knowledge, this is the first report of a patient with motor FND preceding and then coexisting with an eventual diagnosis of rtvFTD. (1) Research project: A. Conception, B. Organization, C. Execution; (2) Statistical analysis: A. Design, B. Execution, C. Review and critique; (3) Manuscript preparation: A. Writing of the first draft, B. Review and critique. I.S.: 1A, 1B, 1C, 3A, 3B A.M.: 1C, 3B E.C.F.: 1A, 1B, 1C, 3B M.R-M.: 1C, 3A, 3B We thank our patient and her spouse for their willingness to publish her case. Ethical Compliance Statement: The authors confirm that institutional review board or ethics committee approval was not required for this case report. The patient's substitute decisionmaker provided written informed consent for publication of the case report. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this work is consistent with those guidelines. Funding Sources and Conflict of Interest: No specific funding was received for this work. The authors declare that there are no conflicts of interest relevant to this work. Financial Disclosures for the Previous 12 Months: I.S. has received funding support from a Canada Institutes of Health Research (CIHR) Canada Graduate Scholarship-Doctoral #193336. E.C.F. has received grant support from the CIHR, the Weston Foundation, the Alzheimer Society of London and Middlesex, and the Physician Services Incorporated Foundation. E.C.F. has served as a scientific advisor for and has received consulting fees from Psilera Inc., Vigil Neuro, and Denali Therapeutics. Author disclosures are available in the Supporting Information. The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions. Data S1. COI_disclosure. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.