A Young Woman With Multiple Sclerosis and Hand Numbness
A 30-year-old woman was diagnosed with multiple sclerosis 8 years earlier when she presented with tingling, paresthesias, and weakness in her arms and legs. MRI showed patchy demyelinating plaques of the brain and spinal cord. Upper and lower extremity somatosensory-evoked responses were abnormal, but visual and brain stem–evoked responses were normal. Her spinal fluid showed evidence of oligoclonal bands and IgG elevation. Treatment with intravenous methylprednisolone produced marked improvement. Six months later, she developed an acute episode of optic neuritis. Repeat MRI showed new enhancing plaques in the brain, whereas the spinal cord lesions had disappeared. There was a complete resolution of symptoms with steroid treatment. Since then, she has had several episodes of exacerbations and remissions characterized mainly by leg numbness, weakness, and vertigo. She is currently on β-interferon therapy.
The patient presented this time with a 3-week history of numbness and paresthesias in the ulnar nerve distribution of the right hand. She denied neck pain or trauma.
Her medical history was unremarkable except for chickenpox infection during childhood. She worked as a secretary and did not smoke or drink alcohol.
Examination revealed normal mentation and cranial nerves except for mild pallor of the right optic disk. Strength was intact except for weakness of the interossei muscles on the right hand with first dorsal interosseous (FDI) muscle wasting. On finger extension, the right fifth digit is adducted and separated from the other fingers ( Fig. 8-1A ) or Wartenberg sign. This is caused by weak third lumbrical and strong hypothenar muscles. This is also seen in more proximal ulnar lesions. Even though the hypothenar muscles are not weak, patients may still have the Wartenberg sign for which the patient did complain of the little finger getting “stuck” when she put her hands in her pocket. She could perform normal “cupping” of the hand indicating a normal palmaris brevis muscle function ( Fig. 8-1B ). The adductor digiti minimi (ADM), thumb, finger, and wrist flexor strength were normal as were all other right upper extremity muscles. There was no focal tenderness in the wrist or elbow. She had decreased sensation in the ulnar nerve distribution involving the palmar surfaces of the fifth digit and ulnar half of the fourth digit; the dorsum of the hand was normal. Adson’s maneuver was negative. There was mild tenderness at the ulnar area of the wrist, but no swelling or masses were detected. No Tinel’s sign was elicited at the elbow or the wrist. Muscle stretch reflexes were normal; there were no Babinski signs. Coordination was normal.
Fig. 8-1
A , Mild atrophy of the first dorsal interosseous and a tendency to adduct the fifth digit when extending the fingers from relatively preserved hypothenar muscles. B , Normal “cupping” of the hand indicating normal function of the palmaris brevis.
What are the Most Likely Possibilities?
This patient had multiple sclerosis, and her recent symptoms could suggest a spinal cord lesion causing numbness and weakness. However, they corresponded to the distribution of the left ulnar nerve, making a spinal cord lesion unlikely. Other possibilities include a C8 radiculopathy or a lesion of the lower trunk or medial cord of the brachial plexus. Ulnar entrapment at the elbow is a consideration as this is the most common site of entrapment of this nerve, but the lack of involvement of the dorsal cutaneous nerve territory and normal palmaris brevis function suggest that the lesion was distal to the elbow.
