Laboratory Studies

Laboratory studies generally are not indicated in the diagnosis of piriformis syndrome.

Imaging Studies

Diagnostic imaging of the lumbar spine may be helpful in excluding associated diskogenic and/or osteoarthritic contributing pathology should conservative treatment of clinically diagnosed piriformis syndrome fail to provide therapeutic benefit.

Reports in the literature on the piriformis muscle describe imaging by nuclear diagnostic studies and MRI of the pelvis,^[17]but these tests are neither practical nor reliable approaches to the diagnosis of piriformis syndrome. The history and clinical diagnostic examination provide the greatest and most specific diagnostic yield for the disorder.

Magnetic resonance neurography

Magnetic resonance neurography is a newer, sensitive imaging technique that increases nerve conspicuity by suppressing the signal from adjacent soft tissue, including fat, bone, and muscle.^[18]The nerve itself contains minimal fat, and its signal is unsuppressed. According to Filler and colleagues, MR neurography demonstrated piriformis muscle asymmetry and sciatic nerve hyperintensity at the sciatic notch with 93% specificity.^[19]The investigators also found that the technique had a sensitivity of 64% with regard to distinguishing patients with piriformis syndrome from persons who, despite having similar symptoms, did not have the condition (p< 0.01).

Ultrasonography

Diagnostic ultrasonographic imaging of the piriformis muscle for the assessment of muscle morphology has demonstrated a significant correlation of piriformis muscle morphology abnormality, especially in patients with lumbosacral/buttock pain and pain ascending stairs, referred pain to the posterior thigh on the symptomatic side, and reproduction of pain with needling of the piriformis muscle.

Other Tests

The results of electrodiagnostic testing for piriformis syndrome usually are normal. Reports of positional H-reflex abnormalities can be found in the literature;^{[20, 21]}however, such findings have not been widely accepted or reproduced.

Treatment & Management

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Media Gallery

Nerve irritation in the herniated disk occurs at the root (sciatic radiculitis). In piriformis syndrome, the irritation extends to the full thickness of the nerve (sciatic neuritis).

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Author

Milton J Klein, DO, MBA Consulting Physiatrist, Heritage Valley Health System-Sewickley Hospital and Ohio Valley General Hospital

Milton J Klein, DO, MBA is a member of the following medical societies: American Academy of Disability Evaluating Physicians, American Academy of Medical Acupuncture, American Academy of Osteopathy, American Academy of Physical Medicine and Rehabilitation, American Medical Association, American Osteopathic Association, American Osteopathic College of Physical Medicine and Rehabilitation, American Pain Society, Pennsylvania Medical Society

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Michael T Andary, MD, MS Professor, Residency Program Director, Department of Physical Medicine and Rehabilitation, Michigan State University College of Osteopathic Medicine

Michael T Andary, MD, MS is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation, American Association of Neuromuscular and Electrodiagnostic Medicine, American Medical Association, Association of Academic Physiatrists

Disclosure: Nothing to disclose.

Chief Editor

Ryan O Stephenson, DO Associate Professor of Clinical Practice, Department of Physical Medicine and Rehabilitation, University of Colorado School of Medicine; Medical Director of Polytrauma and Brain Injury (Polytrauma Network Site), Department of Physical Medicine and Rehabilitation, Eastern Colorado Veterans Affairs Medical Center

Ryan O Stephenson, DO is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation, American Association of Neuromuscular and Electrodiagnostic Medicine, Association of Academic Physiatrists

Disclosure: Nothing to disclose.

Additional Contributors

Rajesh R Yadav, MD Associate Professor, Section of Physical Medicine and Rehabilitation, MD Anderson Cancer Center, University of Texas Medical School at Houston

Rajesh R Yadav, MD is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation

Disclosure: Nothing to disclose.