A Man With Progressive Weakness After a Gastroplasty

A 62-year-old man had gastroplasty for obesity 10 years previously. He presented with progressive weakness in his arms and legs with numbness in his feet for more than 2 months and in his hands for 1 month; he was treated with vitamin supplementation without improvement.

Past medical history included a right ulnar neuropathy at the elbow from trauma. He had a prostatic hypertrophy and a history of anemia from mild myelodysplastic syndrome, diagnosed by bone marrow aspiration, and received weekly erythropoietin infusions. He did not smoke or drink.

Mentation and cranial nerves were normal. There was symmetrical proximal leg weakness of 4/5 in the glutei and iliopsoas, 4+/5 in the quadriceps, 4/5 in the hamstrings and tibialis anterior, and 4+/5 in the peroneal and gastrocnemius. The intrinsic ulnar muscles were wasted and weak in the right hand with 3−/5; neck muscles were normal. Shoulder muscles were 5−/5 in both upper extremities; other muscles were normal. He was areflexic. Sensory examination revealed diminished vibration and position senses in the toes and decreased pinprick sensation to the mid-calf and in the right ulnar nerve distribution. There were no Babinski signs. Coordination and gait were normal. Romberg test was negative. The rest of the examination was normal.

What is the Differential Diagnosis?

This patient had a motor sensory polyneuropathy. He had symmetrical areflexia and proximal and distal weakness suggestive of a demyelinating neuropathy, but the small fibers were also affected. He also had a remote ulnar neuropathy. The possibility of an autoimmune neuropathy, such as chronic inflammatory demyelinating polyradiculoneuropathy, had to be considered, as did, because of his age, a distal acquired demyelinating symmetrical neuropathy, which in some persons could be associated with myelin-associated glycoprotein antibodies, but the proximal weakness was against this possibility. He could also have a nutritional neuropathy associated with the bariatric surgery. The cause of this could include B ₁₂ /folate and thiamine deficiencies. He was not diabetic. Finally, he could have a myeloproliferative disorder causing his neuropathy.

An EMG Test was Performed

Motor Nerve Studies

Nerve and Site	Latency (ms)	Amplitude (mV)	Conduction Velocity (m/s)
Peroneal Nerve R.	Normal ≤ 5.7	Normal ≥ 3	Normal ≥ 40
Ankle	6.2	1	–
Fibular head	13.2	1 ^a	36
Knee	16.6	1 ^a	36

Tibial Nerve L.	Normal ≤ 5.3	Normal ≥ 4	Normal ≥ 40
Ankle	5.9	1.2	–
Pop. fossa	15.5	1.2 ^a	37

Nerve and Site	Latency (ms)	Amplitude (mV)	Conduction Velocity (m/s)
Ulnar Nerve R.	Normal ≤ 3.6	Normal ≥ 8	Normal ≥ 50
Wrist	3.4	7.8	–
Below elbow	7.7	6.9 ^b	48
Above elbow	10.2	5.3 ^b	48

Median Nerve R.	Normal ≤ 4.2	Normal ≥ 6	Normal ≥ 50
Wrist	4.2	10	–
Elbow	8.5	10	47

a Dispersion of waveforms.

b Dispersion of waveforms.

F-Wave and Tibial H-Reflex Studies

Nerve	Latency (ms)	Normal Latency ≤ (ms)
Peroneal nerve R.	55.7	54
Tibial nerve L.	56.8	54
Ulnar nerve R.	32.8	30
Median nerve R.	33.2	30
H-reflex R.	NR	34
H-reflex L.	NR	34

Sensory Nerve Studies

Nerve	Onset Latency (ms)	Normal Onset Latency ≤ (ms)	Peak Latency (ms)	Normal Peak Latency ≤ (ms)	Amp (μV)	Normal Amp ≥ (μV)	Conduction Velocity (m/s)	Normal Conduction Velocity ≥ (m/s)
Sural nerve R.	3.8	3.5	4.2	4.0	6	11	38	40
Ulnar nerve R.	2.7	2.6	3.2	3.1	8	13	49	50
Median nerve R.	2.7	2.6	3.3	3.1	15	20	49	50
Ulnar dorsal cutaneous R.	1.5	1.7	1.9	2.2	5	13	48	50