A 46-year-old man comes to the office with left upper limb weakness and numbness. He has had chronic neck pain since being involved in a motor vehicle collision 4 years ago. He has no other medical problems. Neurological evaluation reveals that the tendon reflex shown in the image below is absent. Reflexes in the right upper extremity and both lower extremities are normal. Imaging studies reveal degenerative changes in the spine causing mild spinal cord compression. Which of the following spinal segments is most likely affected in this patient?

Question

A 46-year-old man comes to the office with left upper limb weakness and numbness.  He has had chronic neck pain since being involved in a motor vehicle collision 4 years ago.  He has no other medical problems.  Neurological evaluation reveals that the tendon reflex shown in the image below is absent.  Reflexes in the right upper extremity and both lower extremities are normal.  Imaging studies reveal degenerative changes in the spine causing mild spinal cord compression.  Which of the following spinal segments is most likely affected in this patient?

Quizplus · Accepted Answer

11ec160b_35c3_5e0b_9249_33439cf11e5e_MD0001_00 This patient has an absent biceps reflex. The test is performed by quickly tapping a reflex hammer against the biceps brachii tendon as it passes through the cubital fossa. This action activates the muscle's stretch receptors that communicate via the musculocutaneous nerve with lower motor neurons in the anterior horn of the C5-C6 spinal level. Axons from these motor neurons return along the musculocutaneous nerve and cause involuntary biceps muscle contraction and jerking of the forearm. The C5-C6 nerves also control the brachioradialis reflex. A stronger than normal reflex suggests an upper motor neuron lesion whereas an absent or decreased reflex indicates a lower motor neuron lesion at the corresponding spinal cord level. (Choice A) The C3-C4 cervical nerves provide innervation to the diaphragm but do not mediate any specific reflexes. (Choices C, D, and E) The C7, C8, and T1 spinal nerve roots form the median and ulnar nerves, which provide motor innervation to the wrist and hand. The T1 and T2 thoracic nerves innervate the rib muscles around the sternum, parts of the axilla, and part of the scapula. However, none of these spinal nerves mediate significant reflexes. Educational objective: The C5-C6 spinal nerves mediate the biceps and brachioradialis reflexes.

A 46-Year-Old Man Comes to the Office with Left Upper