Case 198 Answers

Basic Human Neuroanatomy

A Clinically Oriented Atlas

Case 198 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?

No. The patient’s motor and sensory signs and symptoms do not follow a specific dermatomal or myotomal pattern.

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 peripheral nerve of the right brachial plexus, the long thoracic nerve, while sparing other nerves of the plexus (e.g., the musculocutaneous, axillary, radial, ulnar, median, suprascapular, dorsal scapular, medial and lateral pectoral nerves, etc.). (see below)

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

The patient’s scapular winging and inability to fully abduct the right arm suggest weakness of the serratus anterior muscle due to a lower motor neuron lesion involving the long thoracic nerve (C5, 6, 7).

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

It is difficult to determine the exact location of the lesion in this case, but it is most likely distal to the brachial plexus, since no other part of the plexus and no other branches of the plexus are involved.

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

The patient’s clinical course (pain in the shoulder region, followed by weakness of one or more muscle groups supplied by branches of the brachial plexus) is most consistent with the entity known as “neuralgic amyotrophy” or “brachial neuritis”. This is an idiopathic (rarely, inherited) condition, although various etiologies (viral, inflammatory, autoimmune) have been advanced. Its expression in this patient may have been exacerbated by his carrying a backpack during the two weeks prior to the clear onset of his weakness. Lyme disease must also be considered in view of his tic bite in Massachusetts.

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

References:

1. Parsonage MJ, Turner JWA. Lancet 1948;251:973-978.

2. Tsivgoulis G, Vadikolias K, Courcoutsakis N, et al. Neurology 2012;78:e109.

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