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.