Abstract
Ataxia-telangiectasia is known for cerebellar degeneration, but clinical descriptions of abnormal tone, posture, and movements suggest involvement of the network between cerebellum and basal ganglia. We quantitatively assessed the nature of upper-limb movement disorders in ataxia-telangiectasia. We used a three-axis accelerometer to assess the natural history and severity of abnormal upper-limb movements in 80 ataxia-telangiectasia and 19 healthy subjects. Recordings were made during goal-directed movements of upper limb (kinetic task), while arms were outstretched (postural task), and at rest. Almost all ataxia-telangiectasia subjects (79/80) had abnormal involuntary movements, such as rhythmic oscillations (tremor), slow drifts (dystonia or athetosis), and isolated rapid movements (dystonic jerks or myoclonus). All patients with involuntary movements had both kinetic and postural tremor, while 48 (61%) also had resting tremor. The tremor was present in transient episodes lasting several seconds during two-minute recording sessions of all three conditions. Percent time during which episodic tremor was present was greater for postural and kinetic tasks compared to rest. Resting tremor had higher frequency but smaller amplitude than postural and kinetic tremor. Rapid non-rhythmic movements were minimal during rest, but were triggered during sustained arm postures and goal directed arm movements suggesting they are best considered a form of dystonic jerks or action myoclonus. Advancing age did not correlate with the severity of involuntary limb movements. Abnormal upper-limb movements in ataxia-telangiectasia feature classic cerebellar impairment, but also suggest involvement of the network between the cerebellum and basal ganglia.
Highlights
Ataxia-telangiectasia (A–T) is a recessively inherited multisystem disorder with prominent neurodegeneration, immunodeficiency, radiosensitivity, and enhanced risk for lymphoreticular malignancy
We evaluated abnormal limb movements in A–T with three intents: (1) to quantify the severity of tremor and non-rhythmic adventitious movements, (2) by a cross-sectional approach to determine whether, and to what extent, these movement disorders correlate with increasing age, and (3) to determine whether these movement disorders have specific features that support either a pure cerebellar etiology or are instead better explained by mixed cerebellar and extra-cerebellar correlates
Outside of the cerebellum there is no known consistent pathology, though some animal models of A–T suggest an abnormality of dopaminergic neurons within basal ganglia [13,14]
Summary
Ataxia-telangiectasia (A–T) is a recessively inherited multisystem disorder with prominent neurodegeneration, immunodeficiency, radiosensitivity, and enhanced risk for lymphoreticular malignancy. Motor abnormalities of putative extra-cerebellar origin in individuals with A–T have been noted from the earliest case reports [2,3]. Some of these features, including resting tremor, suggest dysfunction of the basal ganglia. The pathophysiologic basis of other non-rhythmic adventitious movements, such as dystonia and myoclonus could be cerebellar or extra-cerebellar. This uncertainty about the pathophysiology of abnormal motor control is matched by a paucity of literature that quantifies movement disorders in A–T. Patients with disorders prominently affecting the basal ganglia benefit from a different treatment strategy than those with substantial cerebellar involvement
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