A 68 year old woman presents with progressive numbness, tingling and a burning sensation over the outer aspect of her left palm for 3 months, which now radiates to the forearm. On several occasions, she was woken up at night by the pain. There is no history of trauma. She was diagnosed with diabetes 8 years ago, which is well controlled on Metformin.
The fasting plasma glucose level is 100 mg/dl (normal: < 110)
The serum TSH level is 3.8 mU/L (0.4 - 4.5)
The left median nerve shows increased latency in both sensory and motor modalities. Action potential amplitudes and velocities are normal. The left ulnar nerve, and right median and ulnar nerves show normal findings.
You realize that a nerve biopsy is probably not indicated.