|Year : 2015 | Volume
| Issue : 2 | Page : 115-117
A case of piriformis syndrome presenting as radiculopathy
Rammurthy Kulkarni1, Bhavna Borole2, Jaya Chaudhary3, Sushmitha Dev4
1 Department of Anaesthesiology and Pain, Yenepoya Medical College, Mangalore, Karnataka, India
2 Department of Anaesthesiology, Seth. G.S. Medical College (KEM Hospital), Parel, Mumbai, India
3 Department of Anesthesiology and Pain, Medica Superspeciality Hospital, Kolkata, West Bengal, India
4 Department of Anaesthesiology, Apollo Speciality Hospital, Old Mahabalipuram Road, Chennai, Tamil Nadu, India
|Date of Web Publication||15-Apr-2015|
Dr. Rammurthy Kulkarni
"Yashasvi", House no# 6-17-685, Gandhi Nagar 3rd Cross, Mannagudda, Mangalore - 575 003, Karnataka
Source of Support: None, Conflict of Interest: None
Piriformis syndrome has always remained as a diagnostic dilemma because of its varied presentation. Piriformis syndrome is myofascial dysfunction syndrome which causes pain not only because of trigger points within the muscle but also due to peripheral neuritis of the sciatic nerve. The sciatic neuritis is due to compression of the nerve as it passes through the greater sciatic foramen. The symptoms of sciatic nerve entrapment caused by the piriformis syndrome can be easily mistaken for radiculopathy as the nerve entrapment causes pain which radiates down below the knee and can go up to the foot. Electromyography (EMG) and nerve conduction velocity (NCV) studies can help differentiating these two conditions and can eliminate the need for the magnetic resonance imaging (MRI). In this paper, we have reported a case of piriformis syndrome which mimicked S 1 radiculopathy, where diagnosis was confirmed by diagnostic piriformis injection.
Keywords: Electromyography, nerve conduction velocity, piriformis syndrome, radiculopathy
|How to cite this article:|
Kulkarni R, Borole B, Chaudhary J, Dev S. A case of piriformis syndrome presenting as radiculopathy. Indian J Pain 2015;29:115-7
| Case Report|| |
A 60-year-old elderly gentleman visited our clinic with complaints of back pain and left leg pain since 3years. He had predominant back pain which was radiating down the posterior aspect of the left side thigh, leg, up to the lateral foot. The back pain was aggravated on sitting and leg pain aggravated on walking and was comfortable on lying down. He also gave the history of tingling and numbness in the area of leg pain. The pain intensity was 7 out of 10 on numerical rating scale (NRS). The patient was a known diabetic for the past 15 years and was on regular oral hypoglycemics. There was no history of other comorbidities, trauma, infection, or significant weight loss. Patient had consulted a general physician earlier and was prescribed pregabalin 75 mg once a day, which he discontinued after taking for 6 months without any relief.
On examination, straight leg raising (SLR) test was positive on left side at 65°, left side flexion, adduction, internal rotation (FAIR) test was positive and piriformis muscle was tender on palpation. There was also sensory deficit over back of the left leg and along lateral foot. Motor power and ankle reflexes were normal. There were no red flags and examination of other systems was normal. A provisional primary diagnosis of piriformis syndrome was made with a strongly suspicious secondary diagnosis of S 1 radiculopathy as the patient's leg pain was dermatomal and aggravated on walking.
Routine blood investigation, fasting blood sugar, electromyography (EMG), and nerve conduction velocity (NCV) studies were ordered. We did not order for the magnetic resonance imaging (MRI) of the lumbar spine at this point as the radiculopathy was our secondary diagnosis and also because of the cost. Patient was prescribed pregabalin 75mg twice a day and ultracet (combination of paracetamol and tramadol) thrice a day. After 4 days, patient came with the EMG and NCV report which revealed bilaterally absent H-reflex. At this point we ordered for the MRI of the lumbosacral spine which was normal without any evidence of disc herniation. We proceeded with diagnostic piriformis injection which gave a near complete pain relief to the patient and also confirmed our diagnosis.
| Discussion|| |
Symptoms of piriformis syndrome may be caused by referred pain from trigger points in the muscles, by neural and vascular entrapment by the muscle against the greater sciatic foramen, and by sacroiliac joint dysfunction.  The incidence of piriformis syndrome varies widely from 5to 36% with female predominance.  The term piriformis syndrome was first coined by Robinson in 1947, although Freiberg and Vinke described this clinical entity before him. ,, In their classic papers, Freiberg and Vinke defined piriformis syndrome as the triad of positive Lasegue sign, tenderness over the greater sciatic notch and improvement with conservative treatment.  However, they described it as associated with no neurologic signs or positive results from laboratory.  But it has been clearly proved that the piriformis syndrome is often associated with entrapment of sciatic nerve with signs and symptoms of L 5 and S 1 nerve root involvement and electrodiagnostic studies help in the diagnosis and differentiating it from radiculopathies. ,, Piriformis syndrome is notorious in mimicking true S 1 radiculopathy with pain along the posterior thigh and foot. , At times, it becomes clinically difficult to differentiate between these two entities as straight leg raise (SLR) test will be positive even in piriformis syndrome and the FAIR test which is a commonly performed test to diagnose piriformis syndrome has a specificity of 83.2% only.  In such cases, electrodiagnostic studies can be done to distinguish these two pathologies. Fishman and Zybert, in their study concluded that the delay in H-reflex in flexion, adduction, and internal rotation was a simple measure to detect functional sciatic nerve impingement by piriformis muscle. 
In the above mentioned case, we made piriformis syndrome as our first provisional diagnosis because the back pain was aggravated on sitting, FAIR test was positive and on palpation, piriformis was tender. , However, could not rule out the possibility of S 1 radiculopathy as the pain was strictly dermatomal, aggravated on walking, partially relieved on sitting, and there was sensory deficit (numbness) over back of the leg and lateral foot. Numbness is quite uncommon in piriformis syndrome.  We ordered for the EMG and NCV studies of both the lower limbs, which is a less expensive investigation than MRI to confirm the diagnosis of piriformis syndrome and to rule out S 1 radiculopathy. The sensory nerve conduction studies will be abnormal in sciatic nerve neuropathy and normal in root lesions.  EMG of the paraspinal muscles will be abnormal in radiculopathy, but normal in sciatic nerve compression in piriformis syndrome as the paraspinal muscles receive the innervations from the nerves which are branching proximal to the site of sciatic nerve entrapment (i.e., piriformis muscle). ,,
In the EMG and NCV study of our patient, H-reflex was absent bilaterally. EMG study, sensory and motor nerve conductions were normal bilaterally. These findings reflect a more generalized disease such as peripheral neuropathy,  which in this case could be explained by the presence of diabetes mellitus. Still, we opted to go for the MRI of lumbosacral spine because of the patient's clinical presentation which was matching with S 1 radiculopathy and we were not sure whether the EMG of paraspinal muscles was done or not to rule out radiculopathy. The MRI of the spine was totally normal. EMG is very useful in these type of cases, especially where radiculopathy is to be ruled out. In sciatic nerve compression due to piriformis syndrome, NCV can be normal. In such cases, NCV recordings during certain maneuvers like flexion, adduction, and internal rotation can show abnormalities.  This is important in differentiating it from radiculopathy where NCV does not change with limb maneuvers. Unfortunately, these recordings are not routinely done. Thus, requesting the electrophysiologist to perform these studies can help in differentiating these two conditions without any need for MRI. Moreover, MRI can show incidental disc herniations,  which can be misleading and can complicate the scenario. Diagnostic block which is an important weapon of interventional pain physician is also confirmatory.
| Conclusion|| |
Piriformis syndrome is not an uncommon entity to be seen in pain clinics. Its clinical presentation mimics L 5 or S 1 radiculopathy. Careful history, physical examination, and properly conducted EMG and NCV studies can help to differentiate these two conditions and can eliminate the need for more expensive investigations like MRI.
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