Longitudinal brain activation changes related to electrophysiological findings in patients with cervical spondylotic myelopathy before and after spinal cord decompression: an fMRI study

Lumír Hrabálek, Pavel Hok, Petr Hluštík, Eva Čecháková, Tomáš Wanek, Pavel Otruba, Miroslav Vaverka, Petr Kaňovský

Cervical spondylotic myelopathy (CSM) is the most common cause of spinal cord dysfunction, potentially leading to severe disability. Abnormal cervical spine magnetic resonance imaging (MRI) and motor evoked potentials (MEPs) are independent predictors of disease progression. Abnormal MRI is accompanied by various activation changes in functional brain MRI (fMRI), whereas preoperative and postoperative fMRI adaptations associated with abnormal preoperative MEP remain unknown. Twenty patients (9 males, average age 56.6) with evidence of spinal cord compression on MRI and clinical signs of mild CSM were included. Participants were classified according to their preoperative MEP and underwent three brain fMRI examinations: before surgery, 6, and 12 months after surgery while performing repeated extension-flexion of each wrist. Functional MRI activation was compared between two subsets of patients, with normal and clearly abnormal MEP (right wrist: 8 vs. 8; left wrist: 7 vs. 9). At baseline, abnormal MEPs were associated with hyperactivation in the cerebellum. At the first follow-up, further hyperactivations emerged in the contralateral sensorimotor cortices and persisted for 1 year. In normal baseline MEP, activation mostly decreased in the ipsilateral sensorimotor cortex postoperatively. The ipsilateral sensorimotor activation after 1-year follow-up correlated with baseline MEP. Abnormal corticospinal MEP findings in cervical spondylotic myelopathy were associated with differences in brain activation, which further increased after spinal cord decompression and did not resolve within 12-month follow-up. In summary, surgery may come too late for those patients with abnormal MEP to recover completely despite their mild clinical signs and symptoms.