Agnosia for head tremor in essential tremor: prevalence and clinical correlates

Abstract

BackgroundLack of awareness of involuntary movements is a curious phenomenon in patients with certain movement disorders. An interesting anecdotal observation is that patients with essential tremor (ET) often seem unaware of their own head tremor. In the current study, we asked ET patients whether they were aware of head tremor while it was occurring on examination, thereby allowing us to gauge real-time awareness of their involuntary movement.MethodsET cases enrolled in an ongoing clinical research study at the Columbia University Medical Center (2009–2014). During a videotaped tremor examination, they were questioned about the presence of head tremor. True positives were cases who exhibited head tremor on examination and were aware of it; false negatives were cases who exhibited head tremor but were unaware of it.ResultsThe 126 ET cases had a mean age of 72.6 ± 12.4 years. Nineteen (48.7 %) of 39 cases with head tremor on examination did not report having head tremor at that moment. Even among cases with moderate or severe head tremor on examination, unawareness of head tremor was 45.5 %. We assessed the clinical correlates of unawareness of head tremor, comparing true positives to false negatives, and unawareness was correlated with older age, lower mental status test scores and several other clinical variables.ConclusionsNearly one-half of ET cases with head tremor on examination were acutely unaware of their tremor. Whether such agnosia for tremor may be leveraged as a diagnostic feature of ET is a question for future clinical studies.Electronic supplementary materialThe online version of this article (doi:10.1186/s40734-016-0032-0) contains supplementary material, which is available to authorized users.

Essential tremor: diagnosis and management

“…Aside from an action induced tremor, patients with head tremor may have an intention component that can be seen when the patient moves the head forward to sip from a cup 30. A review of videotaped patients with essential tremor found that almost half of patients with head tremor (19/39) were unaware of its presence 31. A study of 51 essential tremor patients with head tremor defined movements as “no-no” (horizontal), “yes-yes” (vertical), or mixed directional 32.…”

Transient, Isolated Head Tremor in “Unaffected” Individuals: Is Essential Tremor an Even More Prevalent Disease Than We Suppose?

“…First, when isolated head tremor was noted on videotaped examination, two additional movement disorder neurologists co-reviewed the videotapes. During this review, head tremor of ET was carefully distinguished from dystonic tremor by the absence of twisting or tilting movements of the neck, jerk-like or sustained neck deviation, or hypertrophy of neck muscles ( 18 ). Head tremor had to be both rhythmic and oscillatory to be ascribed to ET rather than dystonia ( 18 ).…”

“…During this review, head tremor of ET was carefully distinguished from dystonic tremor by the absence of twisting or tilting movements of the neck, jerk-like or sustained neck deviation, or hypertrophy of neck muscles ( 18 ). Head tremor had to be both rhythmic and oscillatory to be ascribed to ET rather than dystonia ( 18 ). Indeed, in this manner, we identified three additional FD-ET with isolated head tremor that we attributed to dystonia.…”

“…The severity of postural and kinetic tremors in the upper extremities was rated (0–3), resulting in a total tremor score (range 0–36, maximum), a measure of the severity of the action tremor. Head tremor was coded as present or absent and was distinguished from dystonic tremor by the absence of twisting or tilting movements of the neck, jerk-like or sustained neck deviation, or hypertrophy of neck muscles ( 18 ). Head tremor had to be both rhythmic and oscillatory to be ascribed to ET rather than dystonia ( 18 ).…”

“…Head tremor was coded as present or absent and was distinguished from dystonic tremor by the absence of twisting or tilting movements of the neck, jerk-like or sustained neck deviation, or hypertrophy of neck muscles ( 18 ). Head tremor had to be both rhythmic and oscillatory to be ascribed to ET rather than dystonia ( 18 ). In those participants with head tremor coded as present on examination by E.D.L., regardless of its severity, the videotaped head tremor was co-reviewed by two additional movement disorders neurologists (A.P., S.T.)…”