Relationship between the anatomic and dermatomal levels of spinal cord tumors in the thoracic region.

In neurologic examination of patients with a suspected compressive lesion at the thoracic region, the dermatomic level of sensory disturbance is the only index indicating the anatomic level of a lesion. Because spinal cord tumors usually are solitary compressive lesions, the relationship between the anatomic and dermatomic levels is conveniently examined. We examined the relationship between the highest dermatomic level of sensory disturbance and the anatomic level, axial location, and type of spinal cord tumors in the thoracic region in 19 patients (8 men and 11 women aged 27-78 years; 11 neurinomas, 7 meningiomas, 1 neurofibroma). The distribution of sensory disturbance was evaluated with 3-g Frey hair and 1-g pin-prick examinations. The dermatomic distribution of sensory disturbance was diagnosed according to the dermatome chart of Keegan and Garrett. The anatomic level and axial location of the tumor were highly related to the sensory disturbance. Eight of 12 tumors in which the dermatomic level of sensory disturbance was within one vertebral segment of the anatomic level were situated in the middle or lower thoracic region (T6-T10). All five tumors in which the dermatomic level was two or more vertebral segments away from the anatomic level were situated at the conus medullaris (T12) or upper thoracic region (T1-T5); the highest level of sensory disturbance was from 4 to 11 segments below the anatomic level of the tumor. In two patients with no sensory disturbance, the tumor was in the upper thoracic region (T5) and compressed the spinal cord from the dorsal side. When a spinal cord tumor at the thoracic region is suspected, imaging examinations should be performed sufficiently cranially.