MRI demonstration of an anterolateral plaque at C1: a note on some sensory changes including analgesia.

A patient developed a partial right-sided Brown-Séquard syndrome at C1. Impairment of left-sided spinothalamic function was associated with abolition of pre-existing left- (but not right-) sided low back pain and sciatica, and prevented the postoperative pain expected after surgery for a benign left-sided breast lump. Later, slight left-sided alteration of light touch appreciation, then allodynia and spontaneous burning pain developed. MRI scanning revealed an isolated abnormality in the right anterolateral quadrant of the spinal cord at C1, consistent with a plaque of demyelination. The site of this abnormality, demonstrated during life and non-invasively, accounted for the partial Brown-Séquard syndrome, the analgesic effects of interrupting spinothalamic pathways, and perhaps the delayed-onset central pain phenomena.