Sciatica & Lumbar Radiculopathy Testing in Sydney
Nerve conduction studies and EMG to localise the level of nerve root involvement — Dr Ron Granot, FRACP, Bondi Junction
Book Your Test NowWhat is Sciatica?
Sciatica is the everyday name for pain radiating from the lower back down the buttock and leg. In most cases, the cause is compression or irritation of a lumbar or sacral nerve root as it leaves the spinal canal — usually at the L5 or S1 level. Less often, the sciatic nerve itself is involved as it passes through the buttock and thigh.
Typical Symptoms by Nerve Root
L5 Radiculopathy
Pain down the outside of the thigh and shin into the top of the foot and big toe. Numbness on the top of the foot. Weakness of foot dorsiflexion — toes catch on the ground when walking (foot drop). Reflexes usually preserved.
S1 Radiculopathy
Pain down the back of the thigh and calf into the heel and outer foot. Numbness on the sole and outer foot. Weakness of plantarflexion — difficulty pushing off when walking, weak calf raise. Reduced or absent ankle jerk.
L4 Radiculopathy
Pain down the front of the thigh into the medial shin. Numbness over the medial calf. Weakness of knee extension. Reduced knee jerk.
Multi-level Involvement
When several nerve roots are involved, the picture overlaps. NCS and EMG can identify which roots are most affected and whether the changes are acute, chronic or recovering.
Why NCS Matters Even When MRI is Already Done
MRI of the lumbar spine is excellent at showing anatomy — disc bulges, foraminal narrowing, facet joint changes. But MRI does not show whether the visible compression is actually injuring a nerve, and many people over 40 have MRI changes without symptoms. NCS and EMG measure nerve function, answering questions MRI cannot:
| Question | What NCS/EMG adds |
|---|---|
| Is this nerve root actually being injured? | EMG shows denervation in muscles supplied by the involved root. |
| MRI shows compression at two levels — which is responsible? | EMG localises the active level by sampling muscles uniquely supplied by each. |
| Is the leg weakness from the back or from the leg itself? | NCS distinguishes radiculopathy from peroneal palsy, peripheral neuropathy, or plexopathy. |
| How long-standing is the nerve injury? | Acute (fibrillations, positive sharp waves) vs chronic (large polyphasic motor unit potentials, reduced recruitment) patterns differ. |
| Has the nerve started recovering since surgery? | Sequential studies track reinnervation — useful when symptoms persist post-operatively. |
The Big Differential — Sciatica vs Peroneal Palsy
Foot drop is a common presentation and the two leading causes — L5 radiculopathy from the back and peroneal palsy at the side of the knee — can look similar on initial examination. Getting this distinction right matters because management is completely different.
| Feature | L5 Radiculopathy | Peroneal Palsy |
|---|---|---|
| Site of compression | L5 nerve root at the spine | Common peroneal nerve at the fibular head (side of knee) |
| Triggered by | Disc, stenosis, lifting injury | Crossing legs, weight loss, prolonged squat, knee surgery |
| Back pain | Often present | Usually absent |
| Hip abductor (gluteus medius) weakness | Often present | Spared (not supplied by peroneal nerve) |
| Tibialis posterior weakness | Often present | Spared |
| NCS — conduction block across fibular head | Absent | Present |
| EMG — paraspinal denervation | Often present | Absent |
See also: Peroneal Neuropathy & Foot Drop
What to Expect at Your Test
Brief clinical assessment
Dr Granot reviews your symptoms, examines you (including reflexes, strength, sensation, straight leg raise), and confirms what the test needs to answer.
Nerve conduction studies
Surface electrodes record motor and sensory responses from leg nerves — peroneal, tibial, sural and superficial peroneal sensory studies. Brief, mild electrical pulses applied at the ankle, knee and fibular head distinguish radiculopathy from peripheral neuropathy or focal compression.
Needle EMG of leg muscles
A fine needle electrode is used to sample selected muscles supplied by L4, L5 and S1 roots — typically including tibialis anterior, peroneus longus, gastrocnemius, extensor hallucis longus, and gluteus medius. Each muscle takes about a minute. EMG of the lumbar paraspinal muscles confirms the level of root involvement when needed.
Same-day results & report
Findings discussed with you immediately. Formal written report to your referring doctor the same day.
Frequently Asked Questions
Get a Definitive Answer on Your Leg Pain
Same-day results • Expert neurologist • Distinguishes back vs leg vs nerve causes
Book Your Nerve Test Now