RESUMO
PURPOSE: Patients with mucopolysaccharidosis type IVA (MPS IVA) have many risk factors for myelopathy and paresis. These are spinal cord compression, bone stenosis, and soft tissue thickening with ligament laxity, deformity, odontoid hypoplasia, and atlantoaxial instability. Although most patients with MPS IVA appear generally healthy at birth, patients often show skeletal deformities within a few years. Surgical indications are difficult to determine. Historically, many physicians have used prophylactic decompression and fusion in young, asymptomatic MPS IVA patients to prevent cord compression. Although spinal cord decompression is usually required at the craniocervical junction in patients with MPS IVA, decompression may be required at other spinal cord levels as well. There is a risk of developing neurological damage during surgery. The most common causes are ischemia secondary to cardiac output deteriorated in the prone position or due to artery damage, and local trauma due to neck movements or traction while bringing the patient to the prone position. Neurophysiological monitoring is very important during surgery to reduce the risk of neurological damage in spinal cord surgery. In this case report, a case with loss of lower extremity neuromonitorization motor evoked potential (MEP) responses in the early period of surgery without any intervention to the craniocervical junction after prone positioning will be presented.