Pure sensory stroke caused by a pontine infarct. Clinical, radiological, and physiological features in four patients.

BACKGROUND AND PURPOSE We conducted this retrospective study to evaluate the clinical, neuroradiological, and neurophysiological findings in patients with pure sensory stroke due to pontine lacuna. SUMMARY OF REPORT Four patients with pontine lacuna, three men and one woman (mean age, 64.5 years; range, 55 to 75 years), were evaluated. Magnetic resonance images were obtained with a 0.5-T superconducting magnet using the SE technique. Short-latency somatosensory evoked potentials were evaluated by unilateral stimulation of the median nerve at the wrist. These tests were done at a mean of 22.5 months (range, 9 to 34 months) after symptom onset. Deep sensory disturbances were present in one half of the patient's body with no other neurological deficits found. The sensory deficit was characterized by a prolonged period of refractory dysesthesia and a discrepancy between the superficial and deep sensory disturbances. Lesions were localized in the medial lemniscus of the middle and lower pons, with a sparing of the spinothalamic tracts. The central conduction times of short-latency somatosensory evoked potentials were prolonged (patients 1, 2, and 4), and the amplitudes were significantly reduced (patients 1 and 2) when stimulating the paresthetic-sided median nerve (contralateral side of the lesion) compared with stimulating the other side. CONCLUSIONS In all cases, the clinical and radiological findings indicated a dysfunction of the medial lemniscal tract in the pons. The observed somatosensory evoked potentials were probably related to the persistent refractory dysesthesias present in these patients.