1. Is there evidence of spinal cord involvement in this case and, if so, at what level?
No
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 three specific terminal peripheral nerves of the left brachial plexus, the median, ulnar, and radial nerves, while sparing other nerves of the plexus (e.g., the axillary, musculocutaneous, other more proximal nerves of the plexus). (see below)
4. Indicate the level of the neurologic lesions in this case and the structures involved by the pathologic process.
Initial numbness, tingling, and pain in the left hand, which was relieved by the carpal tunnel release procedure, and the residual weakness of the thenar eminence muscles indicate involvement of the left median nerve.
Mild sensory impairment involving the palmar aspect of the fourth and fifth fingers and the profound weakness of the intrinsic hand muscles, including the hypothenar muscles, and the flexor carpi ulnaris muscle suggest a lesion of the left ulnar nerve.
The profound weakness of the extensor muscles distal to the supinator muscle suggests a lower motor neuron lesion involving the left radial nerve.
5. Where is the anatomical location of the pathologic process leading to this patient’s condition?
In this patient, the history and clinical examination suggest a multifocal process involving three peripheral nerves (i.e., multiple mononeuropathies or mononeuritis multiplex).
By examination and response to carpal tunnel release, her median neuropathy appears to be at the level of the wrist (i.e., carpal tunnel syndrome) and was produced by placing her wrist in the flexed position in her original cast.
Her radial neuropathy appears to be localized to the proximal forearm, distal to the branches to the brachioradialis, extensor carpi radialis, and supinator muscles, but proximal to those supplying the remainder of the radial innervated muscles (that is, at the point where the deep radial nerve enters the supinator muscle and passes between its superficial and deep layers [i.e., the radial tunnel]). This is a common site of compression of the deep radial nerve.
Her ulnar neuropathy most likely is also in the proximal forearm, either behind the medial epicondyle of the humerus and/or between the two heads of the flexor carpi ulnaris muscle (i.e., the cubital tunnel), since the flexor carpi ulnaris muscle is weak.
6. In general, what type of pathological process do you think is involved in this case?
The most likely pathological process in this setting is a compression or pressure neuropathy due to the casts used to treat her wrist fracture. However, multiple mononeuropathies can also be due to amyloid or tumor infiltration and ischemic, infectious, or inflammatory processes such as diabetes, leprosy, sarcoidosis, vasculitis, and autoimmune diseases.
7. What diagnostic procedure(s) would you undertake at this point?
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