Patterns of sensory dysfunction in lateral medullary infarction. Clinical-MRI correlation.

Sensory dysfunction in lateral medullary infarction (LMI) has been insufficiently studied. We prospectively analyzed the sensory signs of 50 consecutive patients with LMI, correlating them with MRI results. The classical ipsilateral trigeminal-contralateral body/limb pattern was observed only in 13 patients (26%) with lesions confined to the most posterolateral part of the caudal-middle medulla, whereas the bilateral trigeminal pattern observed in 12 patients was associated with large, ventrally extending lesions usually at the middle-rostral medulla. The contralateral trigeminal pattern was observed in nine patients with lesions sparing the most posterolateral area of the medulla. Isolated body/limb and isolated trigeminal involvement were observed in 10 and four patients respectively, usually associated with very small lesions. No sensory sign was noted in two patients. In addition to impaired sensation of spinothalamic modalities, six patients had decreased vibratory sensation in the hypoalgesic body/limb, whereas four patients had a lemniscal sensory deficit on the side contralateral to the hypoalgesic body/limb. Fifteen patients showed sensory gradient or level at the body/limb, and five had delayed appearance of sensory deficits. Trigeminal sensation was usually inhomogeneously involved among three divisions, which was more often of an onion-skin pattern than a divisional pattern. The perioral area, or V3, was generally spared or less severely involved on the side contralateral to the lesion. The sensory manifestations of LMI are extremely diverse and usually, although not always, correlate with MRI findings. The so-called classic, dissociated sensory pattern is actually uncommon, whereas sensory patterns previously thought of as atypical are relatively frequent.