Article

Unverricht-Lundborg disease (ULD) is the most common form of
progressive myoclonus epilepsy. Cerebellar dysfunction may appear over time,
contributing along with myoclonus to motor disability. The purpose of the present
work was to clarify the motor and neurophysiological characteristics of ULD patients. METHODS:
Nine patients with genetically proven ULD were evaluated
clinically (medical history collected from patient charts, the Scale for the
Assessment and Rating of Ataxia and Unified Myoclonus Rating Scale).
Neurophysiological investigations included EEG, surface polymyography, long-loop
C-reflexes, somatosensory evoked potentials, EEG jerk-locked back-averaging
(JLBA) and oculomotor recordings. All patients underwent brain MRI.
Non-parametric Mann-Whitney tests were used to compare ULD patients' oculomotor
parameters with those of a matched group of healthy volunteers (HV). RESULTS:
Myoclonus was activated by action but was virtually absent at rest and poorly
induced by stimuli. Positive myoclonus was multifocal, often rhythmic and of
brief duration, with top-down pyramidal temporospatial propagation. Cortical
neurophysiology revealed a transient wave preceding myoclonus on EEG JLBA (n=8),
enlarged somatosensory evoked potentials (n=7) and positive long-loop C-reflexes
at rest (n=5). Compared with HV, ULD patients demonstrated decreased saccadic
gain, increased gain dispersion and a higher frequency of hypermetric saccades
associated with decreased peak velocity. CONCLUSION: A homogeneous motor pattern
was delineated that may represent a ULD clinical and neurophysiological
signature. Clinical and neurophysiological findings confirmed the pure cortical
origin of the permanent myoclonus. Also, oculomotor findings shed new light on
ULD pathophysiology by evidencing combined midbrain and cerebellar dysfunction.
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Langue : ANGLAIS