Case XXII: Thigh Weakness

(1)

Department of Neurosurgery, University of Wisconsin, Madison, WI, USA

22.1 Case Presentation

An 18-year-old female complains of weakness and decreased bulk of her right thigh. This started 2 years ago with decreased strength of her knee extension. She progressively noticed loss of muscle mass in her thigh as well as weakness in her hip flexors. She also has numbness on the inner aspect of the right leg but no pain. PMH significant for asthma. FH positive for spinal stenosis in her father, type 2 diabetes in the paternal grandmother and “a nerve problem” in 2 aunts. Examination reveals significant atrophy of the right quadriceps with 4/5 strength, right iliopsoas 4/5, and an absent right knee jerk. Sensation is decreased to light touch on the medial aspect of the leg (saphenous n distribution). There is no Tinel’s sign or palpable masses.

22.2 Questions

1.

What is the differential diagnosis?
2.

What studies do you need?

Answers

1.

Differential diagnosis includes: right L4 radiculopathy (less likely in the absence of pain) or femoral neuropathy. The latter could be caused by entrapment (but there is no pain), tumor, diabetic mononeuropathy (grandmother is diabetic but the patient is not), or hereditary neuropathy with liability to pressure palsy (HNPP ) (family history of “a nerve problem”, but HNPP usually affects more distal nerves) [1].
2.

EMG / NCS .

22.3 Questions

3.

EMG/NCS: Absent right saphenous n SNAP, right femoral CMAP had slightly prolonged distal latencies with marked drop in amplitude. Active denervation with marked decrease recruitment in the right quadriceps . The right iliopsoas had slight decreased recruitment but no active denervation. All other muscles including paraspinals were within normal limits.

What do you think is going on?
4.

What do you want to do next?