Case 197 Answers

Basic Human Neuroanatomy

A Clinically Oriented Atlas

Case 197 Answers

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

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?

Unlikely. The patient’s motor and sensory signs and symptoms do not follow a specific dermatomal or myotomal pattern. Although the patient’s signs and symptoms appear to suggest a C8-T1 pattern of involvement, the splitting of the sensory deficit of the fourth finger and the absence of thenar eminence muscle weakness do not support this possibility.

3. Is there evidence of plexus or peripheral nerve involvement in this case, and, if so, how would you differentiate between the two? What evidence is there to support one or the other site of lesion in this case?

Yes. The patient’s signs and symptoms suggest involvement of a specific terminal peripheral nerve of the right brachial plexus, the ulnar nerve, while sparing other nerves of the plexus (e.g., the musculocutaneous, axillary, radial, and median nerves). (see below)

4. Indicate the level of the neurologic lesion in this case and the structures involved by the pathologic process.

Diminished pinprick and touch perception over the right medial palm, the fifth finger, and the medial half of the fourth finger indicates involvement of the ulnar nerve (C8, T1).

The weakness and atrophy of the right hypothenar muscles and the palmar and dorsal interosseous muscles suggest a lower motor neuron lesion involving the ulnar nerve (C8, T1).

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

The presence of the positive “Tinel sign” (paresthesias elicited by tapping a damaged peripheral nerve) produced by tapping over the right ulnar nerve behind the medial epicondyle of the humerus suggests the location of the lesion to be posterior to the medial epicondyle and/or between the two heads of origin of the flexor carpi ulnaris muscle (i.e., the cubital tunnel).

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

Most likely, this patient’s ulnar mononeuropathy is a compression or pressure neuropathy, exacerbated by the patient’s weight loss over the previous several months. However, in view of her multiple medical problems, vascular (ischemic), inflammatory, and nutritional causes must be considered.

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

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