[Diagnostic value of short latency somatosensory evoked potentials for various intracranial lesions]

Diagnostic value of short latency somatosensory evoked potentials (SSEP) was studied in 124 patients with various intracranial lesions. Abnormal SSEPs were recorded in 58 of 124 patients (46.8%) and were classified into three types. Type I (6 cases) showed abnormality of late components with N18 being preserved. All patients with type I abnormality had cortical or subcortical lesions in the parietal lobe. Type II (20 cases) was characterized by abnormality of N18 and late components with N16 being preserved, and mainly seen in patients with a lesion involving thalamus and internal capsule. Type III (31 cases) showed abnormality of N16 and N18 which was elicited by unilateral stimulation (IIIa: 11 cases), or bilateral stimulation (IIIb: 21 cases), and this indicated brainstem impairment. The incidence of SSEP abnormality was as high as 93.1% in patients with sensory disturbance, and 23.1% in patients without such disturbance, and it was suggested that SSEP is useful to detect subclinical dysfunction in the somatosensory pathway. The SSEP grades defined by Anderson et al were found to be well correlated with the outcome of patients with severe head injury, and the SSEP was more reliable for predicting the outcome of patients than the auditory brainstem evoked responses. The SSEP grades were also fairly well correlated with the outcome of patients with cerebrovascular accidents, although the outcome was not consistent in patients with moderately abnormal SSEP.