Acute piriformis syndrome mimicking cauda equina syndrome: illustrative case

Abstract

Background: This report depicts a rare case of acutely developed urinary retention as well as sensory and motor disturbances caused by formation of a large hematoma within the piriformis muscle, which caused compression of nerves within the suprapiriform and infrapiriform foramina, thus imitating cauda equina syndrome. Although cases of acute lumbosacral plexopathy have been described, this case is the first time both urinary retention and sensory and motor disturbances were present.

Observations: The most useful tools for diagnosis of acute piriformis syndrome are detailed patient history, magnetic resonance imaging (MRI) of the pelvic region, and electrophysiological testing performed by an experienced electrophysiologist. As a result of diligent rehabilitation, including physiotherapy and electrostimulation, the patient was able to successfully recover, regardless of acute compression of the sacral plexus that lasted 6 days.

Lessons: Clinicians should actively ask about previous pelvic trauma when taking a patient history in similar cases, especially if the patient is receiving anticoagulation treatment. If MRI of the lumbar spine does not reveal any pathologies, MRI of the pelvic region should be performed. Acute surgical decompression is crucial for preserving neurological function. In similar cases, it is possible to differentiate between spinal cord, cauda equina, and pelvic lesions using electrophysiological studies.

Keywords: CES = cauda equina syndrome; CMCT = central motor conduction time; CT = computed tomography; EMG = electromyography; LSP = lumbosacral plexopathy; MRI = magnetic resonance imaging; PS = piriformis syndrome; cauda equina; lumbosacral plexus; piriformis syndrome; urinary retention.

FIG. 1.

A: Hematoma within the piriformis muscle on axial preoperative CT (white arrow). B: Hematoma within the piriformis muscle on coronal preoperative CT (white arrow). C: Hematoma within the piriformis muscle on axial preoperative MRI T2 true-FISP sequence (white arrow). D: Hematoma within the piriformis muscle on coronal preoperative MRI true-FISP sequence (white arrow).

FIG. 2.

A: Planning of the transgluteal approach using anatomical landmarks (GT = greater trochanter; SIP = superior posterior iliac spine; TI = ischial tuberosity) to identify the piriformis muscle and sciatic nerve (black arrow). B: Dark hematoma within the piriformis muscle (white star). C: Evacuation of the hematoma by incising the piriformis muscle (white star), thus decompressing the sciatic nerve (black star). D: Mobilization of the piriformis muscle (white star) and identification of structures within the infrapiriform foramen: sciatic nerve (black star), inferior gluteal nerve (white arrow), posterior femoral cutaneous nerve (black arrow), and inferior gluteal vessels (white dashed arrow).

FIG. 3.

A: Absent contraction of the left gluteal muscles at the 3-month follow-up. B: Active contraction of the left gluteal muscles at the 6-month follow-up. C: Maximal plantar flexion at the 26-month follow-up. D: Maximal dorsal flexion and toe extension at the 26-month follow-up.