Preventing Motor and Sensory Deficits in an Anterior Cervical Discectomy and Fusion

July 07, 2024

Cervical spinal cord compression caused by central stenosis can have debilitating consequences. Often, this condition results from bone spurs or degenerative disc disease that narrows the spinal canal, pressing on the nerves. This equates to patients experiencing symptoms such as shoulder and arm pain, numbness, tingling, weakness in the upper extremities, and difficulty walking, which can significantly impair a person's quality of life. 

The standard treatment for this condition is anterior cervical discectomy and fusion (ACDF). Intraoperative neuromonitoring (IONM) is critical during these procedures to prevent motor and sensory deficits, making more successful surgical outcomes possible.

One 64-year-old male, presented with chronic back pain accompanied by bilateral upper and lower extremity weakness and paresthesia. A physical examination revealed decreased motor function and sensation in the upper and lower extremities. Further imaging studies confirmed the presence of spinal cord compression at the C4-C5 level. Consequently, the patient was diagnosed with focal motor deficit, focal motor weakness, and C4-C5 spinal cord compression.

Neurophysiological Monitoring During Surgery

Given the complexity and risks associated with the procedure, the surgeon employed multiple IONM modalities, including Somatosensory Evoked Potentials (SSEPs), Transcranial Electrical Motor Evoked Potentials (TCeMEPs), Electromyography (EMG), Train-of-Four (TOF), and Electroencephalography (EEG) to monitor the depth of anesthesia.

Initial traction of 20 lbs was applied to the patient's spine, leading to a significant loss of SSEP and MEP responses in both the upper and lower extremities. Recognizing the danger, the surgeon immediately removed the traction. A reduced traction weight of 10 lbs was then applied, which was maintained for the remainder of the surgery. 

During the discectomy, spontaneous EMG (SEMG) train activity was detected in the right Flexor Carpi Ulnaris (FCU) and Flexor Carpi Radialis (FCR) muscles. Upon being informed of this activity, the surgeon paused the discectomy, allowing the SEMG activity to cease before resuming the procedure.

Following the adjustment of the traction weight, the SSEP and MEP responses returned to approximately 80% of their original values. The reduced traction of 10 lbs helped maintain stable SSEP and MEP readings during the surgery. The surgeon's attentiveness to SEMG activity ensured no further neural damage occurred during the discectomy, leading to a quiet SEMG until the surgical closure.

The Role of IONM

This case underscores the indispensable role of IONM in spinal surgeries. Without the real-time feedback provided by SSEP and MEP monitoring, the initial 20 lbs traction could have compromised the cervical spinal nerves, potentially leading to irreversible sensory and motor deficits post-operatively. By promptly adjusting the traction and responding to neurophysiological feedback, the surgical team was able to avoid significant neural damage and achieve a successful outcome for the patient.

Intraoperative neuromonitoring is a vital tool in modern spinal surgery, providing real-time data that can significantly influence surgical decisions and outcomes. As demonstrated in this case, the ability to detect and respond to neural compromise during surgery can prevent severe postoperative complications, enhancing patient safety and recovery.

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