A 48-year-old, mildly obese man developed burning paresthesias in the outer aspect of the right thigh of an insidious onset. This increased when he was working. He denied weakness or other neurologic problems.
Past medical history was unremarkable. Family history was noncontributory; the patient drank moderately.
Examination revealed normal mentation and cranial nerves. Motor examination was normal. Reflexes were normal and equal. There was a patchy area in the right lateral thigh where he had an unusual sensation when touched and felt somewhat numb when compared with the rest of the leg or the other side. The examination was otherwise unremarkable.
What is the Differential Diagnosis?
A lumbar radiculopathy, plexopathy, or femoral neuropathy should be included in the differential diagnosis, but the lack of back pain, weakness, and normal reflexes make these unlikely. The symptoms suggest a lateral femoral cutaneous neuropathy.
What Tests should be Ordered?
A complete metabolic panel, a 2-hour postprandial blood sugar test, and the sedimentation rate were normal.
An EMG Test was Performed
| Nerve and Site | Latency (ms) | Amplitude (mV) | Conduction Velocity (m/s) |
|---|---|---|---|
| Peroneal Nerve R. | Normal ≤ 5.7 | Normal ≥ 3 | Normal ≥ 40 |
| Ankle | 3.7 | 8 | – |
| Fibular head | 10.9 | 8 | 45 |
| Tibial Nerve R. | Normal ≤ 5.3 | Normal ≥ 4 | Normal ≥ 40 |
|---|---|---|---|
| Ankle | 4.7 | 6 | – |
| Pop. fossa | 14.3 | 6 | 42 |
| Nerve | Latency (ms) | Normal Latency ≥ (ms) |
|---|---|---|
| Peroneal nerve R. | 50.2 | 54 |
| Tibial nerve R. | 51.2 | 54 |
| H-reflex R. | 33.0 | 34 |
| H-reflex L. | 32.8 | 34 |
| Nerve | Onset Latency (ms) | Normal Onset Latency ≤ (ms) | Amp (μV) | Normal Amp ≥ (μV) |
|---|---|---|---|---|
| Sural nerve R. | 3.8 | 4.0 | 21 | 11 |
| Lat. fem. cut. R. | NR | 3.6 | NR | 3–10 |
| Lat. fem. cut. L. | 3.5 | 3.6 | 10 | 3–10 |
| Muscle | Insrt Activity | Fibs | Pos Waves | Fasc | Amp | Dur | Poly | Pattern |
|---|---|---|---|---|---|---|---|---|
| Lumbar paraspinal R. | Norm | None | None | None | Norm | Norm | None | Full |
| Tensor fasciae latae R. | Norm | None | None | None | Norm | Norm | None | Full |
| Biceps femoris, long head R. | Norm | None | None | None | Norm | Norm | None | Full |
| Tibialis anterior R. | Norm | None | None | None | Norm | Norm | None | Full |
| Gastrocnemius R. | Norm | None | None | None | Norm | Norm | None | Full |
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