Basic Human Neuroanatomy
A Clinically Oriented Atlas 
Case 5 Answers

1.  Is there evidence of spinal cord involvement in this case and, if so, at what level(s)?


2. Is there evidence of dorsal or ventral root involvement or spinal nerve involvement in this case, and, if so, what is the level(s) of the involvement?

No. Even though the patient had neck pain and stiffness, and the sensory symptoms radiated up into the forearm when severe, the persistent core of the patient’s motor and sensory signs and symptoms does not follow a specific dermatomal or myotomal pattern.

3. Is there evidence of plexus or peripheral nerve involvement in this case? If so, indicate the specific structure(s) involved by the pathologic process.

Yes. The patient’s signs and symptoms suggest involvement of a specific peripheral nerve of the right brachial plexus, the median nerve, while sparing other nerves of the plexus (e.g., the axillary, musculocutaneous, ulnar, and radial nerves, and more proximal nerves of the plexus). Numbness and tingling involving the anterior(palmar) aspect of the lateral 3½ digits of the right hand, plus mild weakness of the abductor pollicis brevis and flexor pollicis brevis muscles, suggest a lesion of the right median nerve.

4. Where is the anatomical location of the pathologic process leading to this patient’s condition?

His right median mononeuropathy appears to be localized to the wrist where the nerve passes deep to the flexor retinaculum along with the tendons of the flexor pollicis longus, flexor digitorum superficialis, and flexor digitorum profundus muscles (i.e., the carpal tunnel). The median nerve innervated muscles in the forearm are spared. In addition, there are no sensory signs or symptoms involving the palm of the hand, indicating that the palmar cutaneous branch of the median nerve is intact. This nerve branches off the median nerve just proximal to the flexor retinaculum.

5. In general, what type of pathological process do you think is involved in this case?

The carpal tunnel is the most common site of compression of the median nerve, and, in fact, carpal tunnel syndrome is the most common nerve entrapment syndrome. Carpal tunnel syndrome usually is caused by excessive, repetitive use of the hands and occupational trauma. It is more common in the dominant hand. Other less common causes include diabetes, amyloid infiltration, autoimmune disorders (especially rheumatoid arthritis), acromegaly, hypothyroidism, and pregnancy.

6. What diagnostic procedure(s) would you undertake at this point?

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