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Review Question - QID 211729

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QID 211729 (Type "211729" in App Search)
A 63-year-old male undergoes a C4-C7 posterior fusion and laminectomy secondary to significant spinal cord stenosis. Pre-operative examination reveals neck pain, spasticity signs, and finger clumsiness. Post-operative day one, he complains of significant weakness with raising his left arm overhead and on further examination, you notice a clear sensation deficit over the lateral shoulder. What is the most commonly affected structure?

C4 nerve root

3%

74/2285

Suprascapular nerve

1%

26/2285

Axillary nerve

9%

199/2285

C6 nerve root

2%

43/2285

C5 nerve root

84%

1929/2285

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The patient in this question has signs of cervical myelopathy and underwent posterior cervical fusion and laminectomy from C4-7 and is suffering from symptoms of a C5 nerve root palsy based on his post-operative examination with shoulder weakness and lateral shoulder sensation deficit. A C5 nerve root palsy is the most commonly affected structure with this surgery.

The exact mechanism of C5 nerve root injury is controversial. However, the risk of a C5 nerve root palsy exists with both anterior and posterior cervical spinal surgeries. Symptoms of a C5 nerve root palsy would be shoulder abduction weakness (supraspinatus, deltoid), elbow flexion weakness (biceps and brachialis), pain in the shoulder area, and sensory deficits around the shoulder. Rates of injury are estimated to be between 0 and 30%.

Nassr et al. retrospectively reviewed 750 multilevel cervical spine decompression surgeries by a single surgeon to identify the risk of C5 palsy. 630 patients were included in the analysis and they found that the mean incidence of C5 palsy was 6.7% with a higher incidence for the posterior laminectomy and fusion group (9.5%) and higher incidence in males. Despite this higher incidence, they concluded that the incidence of C5 palsy was not statistically significant between anterior and posterior procedures.

Eskander et al. looked at vertebral artery anatomy using MRI on 250 patients. They identified three main groups of anomalies being intraforaminal anomalies with midline migration, extraforaminal anomalies(entering in the foramen at a different level), and arterial anomalies. They found that 7.6% of patients had midline migration of the vertebral artery and 92% of vertebral arteries were in their transverse foramen at the C6 level. Ultimately, they concluded that vertebral artery anatomy needs to be carefully considered to avoid injury.

Currier et al. studied the anatomic relationship of the Internal Carotid artery (ICA) to C1 using CTs with contrast. They looked at 50 CTs with contrast to determine the distance of the ICA to C1, which was 2.88mm on the left and 2.89mm on the right. The ICA was at a moderate risk of injury in 46% of cases and high risk in 12% of cases. They concluded that anytime C1 will have a screw placed a CT with contrast is recommended to determine ICA location, its risk of injury, and the need to switch to unicortical fixation.

Incorrect Answers:
Answer 1: C4 nerve root is not the most likely affected structure and does not assist with shoulder abduction or lateral shoulder sensory input.
Answer 2: The Suprascapular nerve has contributions from the C5 nerve root and C6, but is not the most commonly affected structure with this surgery.
Answer 3: The Axillary nerve has contributions from the C5 nerve root and C6, but is not the most commonly affected structure with this surgery.
Answer 4: While the C6 nerve root does provide motor input to the shoulder (Axillary nerve C5, C6), the C5 nerve root is more commonly affected.

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