Piriformis Syndrome and Neuropathic Fibular Pain Caused
by Anomalous Sciatic Anatomy
David
S Younger
David
S Younger, Department of Neurology, New York
University Langone Medical Center, New York University School of Medicine, and
the Global Institute of Public Health, New York University, New York, the
United States
Correspondence to: David S Younger,
MD, MPH, Department of Neurology, New York
University Langone Medical Center, New York University School of Medicine, and
the Global Institute of Public Health, New York University, New York, the
United States
Email: david.younger@nyumc.org
Telephone: +1-212-213-3778
Fax:
+1-212-213-3779
Received: November 19,
2014 Revised: December 26, 2014
Accepted: January 30, 2014
Published online: February 2, 2015
ABSTRACT
A 57-year-old
woman with piriformis syndrome and neuropathic fibular pain was found to have
high branching of the common fibular nerve division of the sciatic nerve above
a bifed piriformis muscle leading to entrapment neuroimaging studies. This was
successfully treated with corticosteroid injection in the vicinity of the
piriformis muscle and along the sciatic perineurial space under
© 2015 ACT. All
rights reserved.
Key words: Piriformis Syndrome; Fibular; Sciatic
Younger DS. Piriformis Syndrome and
Neuropathic Fibular Pain Caused by Anomalous Sciatic Anatomy. International Journal of Neurology Research 2015; 1(1): 18-19 Available from: URL:
http://www.ghrnet.org/index.php/ijnr/article/view/927
INTRODUCTION
Sacro-iliac joint arthritis was a cause of sciatica at the turn of the
last century[1]; however the piriformis muscle, which spans the
joint, became synonymous with sciatica evoked by passive internal rotation, hip
flexion and abduction maneuvers. Piriformis syndrome was ascribed to contact of
the muscle with upper sacral nerves and the sciatic trunk as they transited the
infrapiriformis foramen (IF)[2]. Sectioning a tight iliotibial band[3],
piriformis myotomy and fascial band releases[4], and physiotherapy
have all been advocated as effective modes of therapy. Although over-diagnosed[5],
there are subsets of affected patients with anomalous anatomy.
CASE REPORT
A 57-year-old woman noted left sciatica in 2006 followed lateral left
calf, foot and ankle hyperalgesia and allodynia that was treated with opiod
drugs, local injections into the superficial fibular sensory nerve and surgical
repair of peroneal tendinopathy but without benefit. On neurological
examination in June 2014 there was minimal extensor foot weakness but marked
hyperesthesia along the left lateral calf and dorsum of the foot, without
absent ankle reflex or left sciatic notch palpation tenderness. The right leg
and arms were normal. There were no serological abnormalities suggestive of an
underlying autoimmune, infectious or inflammatory disorder. Electrodiagnostic
studies were consistent with left common fibular neuropathy involving the deep
and superficial divisions with chronic axonal features. Non-contrast magnetic
resonance neurography (MRN) of the pelvis showed a bifid left piriformis muscle
with an intramuscular course of the common fibular nerve division that was
deflected by the inferior piriformis muscle (Figure 1) as well as increased
signal intensity along the nerve at the infrapiriformis foramen. She underwent
ultrasound-guided injection of 1.5 cc betamethasone and 1.5 cc 0.5% ropivacaine
in the vicinity of the piriformis muscle and along the sciatic perineurial
space followed by improved pain.
DISCUSSION
Treatable unilateral sciatica and neuropathic pain has been causally
associated with anomalous anatomy of the piriformis muscle and sciatic nerve. A
study of 168 cadaveric dissections showed division of the sciatic trunk above
the IF into a fibular component that pierced the piriformis muscle leading to
possible entrapment, while the tibial component exited normally[6].
Chen[7] noted sciatic nerve entrapment through a bifed piriformis
muscle at surgical exploration for progressive sciatic neuropathy in one
patient who improved with surgical resection of the lower muscle belly. There is a rat model of sciatic mononeuropathy
due to experimental chronic constriction injury in which morphological and
functional nerve changes were associated with hyperalgesia and allodynia
similar to the distal fibular neuropathic complaints in the present patient[8].
CONFLICT OF INTERESTS
The Author has no conflicts of interest to declare.
REFERENCES
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behavior in the rat. Acta Neuropathol 2002; 104: 137-143
Peer reviewer: Janny
Sun, Emeritus Professor, Hong Kong, Editor-In-Chief of International Journal of
Neurology Research, ACT Publishing Group Limited Company.
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