Intramedullary melanotic schwannoma: a rare presentation of a rare tumor. Illustrative case.

BACKGROUND: Intramedullary melanotic schwannomas (IMSs) are rare spinal cord tumors, and a hemorrhagic IMS is an even rarer presentation of this uncommon lesion. The authors describe the second known case of a hemorrhagic IMS and briefly review the characteristics of IMSs. OBSERVATIONS: The patient's initial presentation and imaging indicated an intramedullary thoracic spinal cord tumor impairing lower extremity function. Intraoperatively, the lesion appeared pigmented and hemorrhagic. Pathologic analysis determined the tumor to be an IMS. LESSONS: Melanotic schwannomas vary in presentation and can resemble malignant melanoma but are differentiated by pathologic markers. Lesions typically present as extramedullary masses in the thoracic cord. Intramedullary presentation is rare but should be considered for pigmented tumors.

Somatosensory corticospinal tract axons sprout within the cervical cord following a dorsal root/dorsal column spinal injury in the rat.

The corticospinal tract (CST) is the major descending pathway controlling voluntary hand function in primates, and though less dominant, it mediates voluntary paw movements in rats. As with primates, the CST in rats originates from multiple (albeit fewer) cortical sites, and functionally different motor and somatosensory subcomponents terminate in different regions of the spinal gray matter. We recently reported in monkeys that following a combined cervical dorsal root/dorsal column lesion (DRL/DCL), both motor and S1 CSTs sprout well beyond their normal terminal range. The S1 CST sprouting response is particularly dramatic, indicating an important, if poorly understood, somatosensory role in the recovery process. As rats are used extensively to model spinal cord injury, we asked if the S1 CST response is conserved in rodents. Rats were divided into sham controls, and two groups surviving post-lesion for ~6 and 10 weeks. A DRL/DCL was made to partially deafferent one paw. Behavioral testing showed a post-lesion deficit and recovery over several weeks. Three weeks prior to ending the experiment, S1 cortex was mapped electrophysiologically, for tracer injection placement to determine S1 CST termination patterns within the cord. Synaptogenesis was also assessed for labeled S1 CST terminals within the dorsal horn. Our findings show that the affected S1 CST sprouts well beyond its normal range in response to a DRL/DCL, much as it does in macaque monkeys. This, along with evidence for increased synaptogenesis post-lesion, indicates that CST terminal sprouting following a central sensory lesion, is a robust and conserved response.