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.

Department of Anatomy 2nd Faculty of Medicine Prague Charles University Prague Czech Republic

Departments of Neurosurgery and

Faculty of Medicine in Plzeň Charles University Plzeň Czech Republic; and

Neurology J E Purkyne University Masaryk Hospital Krajská Zdravotní a s Ústí nad Labem Czech Republic

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