Rhythmic axial reflex myoclonus

Preceded by multiple minor strokes, a subclavian steal syndrome, and severe claudication, a 72 year old patient became paraparetic, incontinent, and d eveloped rhythmic trunk jerks whenever she tried to maintain an erect sitti ng or standing position. At presentation, the first impression was that of an unusual postural tremor. However, the jerks could be elicited by taps to the back, which revealed them as myoclonus. Stimulus-triggered polymyograp hy showed 3/s bursts lasting between 100 and 200 ms. Latency varied between 57.2 and 91.6 ms (median: 64 ms) after upper thoracic, and between 62 and 84 ms after lumbar stimulation. irrespective of stimulus site, the jerks in the sternocleidomastoid muscles preceded those in the lower back paraspina l muscles by 35 +/- 8 ms. The cranio-caudal propagation velocity was estima ted to be 17 m/s. Jerking stopped earlier in the lower segments. Like a ret icular reflex myoclonus, the myoclonus obviously originated in the medulla oblongata, but travelled downwards much slower, and spared limbs and masset er. Propagation velocity, burst duration and rhythmicity rather resembled p ropriospinal myoclonus. The myoclonus of our patient thus combined features of propriospinal and reticular relfex myoclonus. It responded to clonazepa m 2 mg/d. The cause remained unclear. As there was no neuromuscular explana tion for the associated paraparesis, a myelopathy was assumed, either vascu lar, or inflammatory. The CSF had oligoclonal bands and serology suggested a legionella infection. IgC anti campylobacter jejuni antibodies were posit ive.