Obturator neuropathy - secondary to compressive acetabular paralabral cyst
Presentation
Longstanding right medial thigh pain with normal lumbar spine MRI, no history of pelvic trauma or surgery.
Patient Data
A polylobed cystic lesion is seen in the inferomedial aspect of the right acetabulum that communicates with the joint space and extends along the course of the obturator nerve in keeping with a compressive paralabral cyst.
Volume loss with T2 fat sat high signal intensity concerning the right adductor magnus, adductor longus, adductor brevis and gracilis consistent with fatty atrophy secondary to chronic denervation.
Annotated images:
the first image illustrates the right adductor muscles fatty atrophy compared to the contralateral side
the second image indicates the right acetabular paralabral cyst
Case Discussion
The denervation pattern is suggestive of obturator neuropathy. The diagnosis of obturator neuropathy should be confirmed by electromyography 1.
Obturator neuropathy is an uncommon neuropathy of the lower extremity. It occurs most commonly as a perioperative complication (total hip arthroplasty, pelvic or abdominal procedures) or is associated with pelvic trauma. The other causes of obturator neuropathy include: inappropriate lithotomy position, pelvic tumor infiltration, and entrapment neuropathy observed in athletes, which is caused by fascial entrapment of the obturator nerve where it enters the thigh 1.
Obturator neuropathy caused by an acetabular paralabral cyst is very rare, and only few cases have been reported in the literature 1.
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