[Pseudoradicular sensory impairment caused by parietal lesions: report of two cases]

Here we report two cases of pseudoradicular sensory impairment (PRSI) caused by cerebral infarctions. Case on was a 49-year-old male who presented with dysesthesia in the left ulnar nerve distribution, and case 2 was a 57-year-old male who developed dysesthesia and weakness in the left radial nerve distribution. In both cases, the symptoms began with dysesthesia, followed by disturbance of cortical sensation, and distal motor weakness of the left upper extremity. Although the temperature, superficial pain, tactile, and vibratory sensations were well preserved, position sense, and cortical sensations such as two-point discrimination, material discrimination and stereognostic sensations were severely disturbed. No abnormalities were found in nerve conduction studies or cervical magnetic resonance imaging (MRI). Findings of somatosensory evoked potential (SEP) indicated that cortical components (N20, P24, N35 and P55) were missing in the left ulnar nerve in case 1, and in the median nerve in case 2. MRI of the brain revealed cerebral infarctions in the right parietal lobe including the postcentral gyrus. From the above results sensory disturbances of these two cases are caused by infarctions of the right parietal lobe. The characteristics of sensory disturbances caused by parietal lesions in our cases are similar to the previous reports. In addition, we found that the impaired cortical and subcortical areas were larger than the predicted areas indicated by Penfield's somatosensory homunculus. From the thermography, we found that the dermal regions with sensory impairment were more or less hypothermal. This suggests that cortical and subcortical infarctions may lead to localized sympathetic dysfunctions of the skin.