Inverted supinator test: How to perform and interpret it

The inverted supinator test is a quick reflex check for cervical myelopathy, which is compression of the spinal cord in the neck. You tap the brachioradialis tendon near the wrist and watch the forearm and fingers together.

A positive result pairs a weak or absent forearm jerk with an unexpected flick of the fingers. That pattern points to an upper motor neuron lesion at or above C5-C6, rather than a pinched nerve root. A 2024 case report in Annals of Internal Medicine: Clinical Cases describes the sign.

Miss it, and a patient with a compressed cord may leave with a neck-stretch handout instead of an MRI request. Below, we cover the anatomy, technique, grading, documentation and referral.

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Key takeaways

A positive inverted supinator test pairs an absent or reduced brachioradialis reflex with reflex finger flexion.

The pattern suggests an upper motor neuron lesion at or above C5-C6, which separates cord compression from a C6 root problem.

Reported specificity is high (78-99%) but sensitivity is low and variable, so a negative test never rules out myelopathy.

Grade the brachioradialis on the 0-4+ scale and record finger flexion separately for each side, so serial exams stay comparable.

Practice software such as Pabau keeps customizable assessment forms and structured client records together for physical therapy and musculoskeletal practices.

The inverted supinator test checks two reflex pathways with one tap

The inverted supinator test is a deep tendon reflex exam that looks for cervical cord compression. One tap on the brachioradialis tendon checks two things. First, it tests the C5-C6 reflex arc that bends the elbow and turns the forearm. Second, it shows whether the finger flexors below that level have lost their normal brake.

You’ll also see it called the inverted supinator sign, the inverted radial reflex or the inverted brachioradialis reflex. All of these names describe the same finding. It belongs in the same toolkit as the Hoffmann sign, the Babinski sign and clonus.

A normal tap makes the forearm supinate and the elbow flex slightly. In a positive test, that movement fades or disappears, and the fingers flex instead. You need both halves of the pattern, because either one alone means something different.

Why the reflex inverts: A broken arc above an overactive one

The brachioradialis muscle drives the supinator reflex. Its sensory signal enters the cord through the C5 and C6 roots. The motor signal travels back out through the radial nerve and bends the elbow.

Compression of the cord at C5-C6 disrupts this loop in two ways. Damage at that segment weakens or abolishes the local reflex, so the brachioradialis barely responds. The same lesion also interrupts the descending corticospinal pathways that normally damp down reflexes below it.

The finger flexors, supplied mainly by C7 and C8, become overactive as a result. The vibration from the tap is enough to trigger them, so the fingers flex.

That dual pattern is why the sign is highly specific for cord-level disease at or above C5-C6. A C6 radiculopathy can also dampen the brachioradialis reflex. However, the descending tracts stay intact, so the fingers stay still. A Spurling’s test and a dermatomal sensory check help confirm a root problem instead.

A positive inverted supinator sign points to the cord, not the root

A positive inverted supinator sign suggests an upper motor neuron lesion at or above C5-C6. The most common cause is degenerative cervical myelopathy, often called cervical spondylotic myelopathy.

Suspect it in patients over 50 who report clumsy hands, dropped objects, trouble with buttons or an unsteady walk. Other causes of cord compression at this level include ossification of the posterior longitudinal ligament and trauma. Less often, demyelinating disease or a cord tumor is responsible.

The sign doesn’t tell you which cause you’re dealing with. What it does tell you is that the lesion sits in the cord, and that the patient needs imaging.

How accurate is the inverted supinator sign? Specific, but easy to miss

Short answer: trust a positive result more than a negative one. A 2025 scoping review in Spinal Cord compared case-control studies of myelopathy signs. Across four studies, the inverted supinator sign showed specificity of 78-99%. Its sensitivity ranged from just 18% to 75%.

A 2022 Neurology teaching case illustrates the inverted radial reflex and the Wartenberg thumb sign in a patient with cervical myelopathy. In practice, a positive result justifies prompt imaging. A negative result does not exclude early myelopathy, so keep testing the other signs.

The chart below shows how much tighter the specificity band is than the sensitivity band, with the Hoffmann sign for comparison.

How to perform the inverted supinator test in five steps

Poor positioning is the easiest way to miss a positive result or create a false one. Set the arm up carefully, then work through the steps on both sides.

Position the arm so it can relax

Seat the patient with the forearm resting on their lap or your hand, and the elbow flexed about 90 degrees. Hold the forearm midway between pronation and supination. Then ask them to let the arm go heavy and not help the movement.

Tap once and watch two places

1. Find the brachioradialis tendon on the thumb side of the forearm, about 5-8 cm above the wrist.
2. Strike it once, briskly, with a Trömner or Queen Square reflex hammer.
3. Watch the forearm and the fingers at the same time, not one after the other.
4. Repeat on the other arm and compare the two sides.
5. If both reflexes seem absent, retest while the patient clenches their teeth to reinforce the response.

You’ll see one of three responses:

• Normal: The forearm supinates and the elbow flexes mildly. Finger flexion is absent or minimal.
• Absent or diminished: Neither the brachioradialis nor the fingers respond. This fits a C5-C6 radiculopathy or a lower motor neuron problem, or simply a naturally hyporeflexic patient.
• Inverted (positive): The brachioradialis response is absent or markedly reduced while the fingers flex. This is the defining positive finding.

A one-sided positive result still counts, especially when it matches the patient’s symptoms. Bilateral positivity, though, raises the urgency considerably.

Reading the result: Negative, equivocal or positive

Read the result from what the tap produces in both places, not just what disappears. Use this reference when you record it.

Grade and document the sign so the next exam can be compared

Myelopathy is often monitored over serial exams before anyone decides on surgery. A note that only says “positive” can’t show whether the sign is getting worse.

Grade the brachioradialis on the standard 0-4+ deep tendon reflex scale. Then record finger flexion separately, as present or absent, for each side.

If several clinicians see the same patient, a shared deep tendon reflex exam template keeps the grading consistent.

A typical positive entry might read: “Left BR reflex 1+/4+, finger flexion present. Right BR reflex 2+/4+, no finger flexion. Repeat in 6 weeks or earlier if symptoms progress.” Kept in structured patient records, that entry lets the next clinician judge the trend without starting over.

Before you document: A quick checklist

• The side tested, and whether you compared both arms
• The brachioradialis grade on the 0-4+ scale
• Finger flexion recorded separately, as present or absent
• Whether you used reinforcement
• Other upper motor neuron signs tested, with their results
• Symptoms, functional limits, and the referral decision with its date

Common mistakes that hide or fake a positive result

Most errors with this test come from technique rather than interpretation. These are the ones to watch for.

• Watching only the forearm: The finger flick is small and quick. If your eyes are on the elbow, you’ll miss the half of the sign that matters.
• Tapping the muscle belly: A strike too high on the forearm hits muscle, not tendon. The response is weak and hard to read.
• A tense arm: A patient who holds the arm up or helps the movement damps the reflex. Support the forearm fully.
• Calling brisk reflexes inverted: Finger flexion alongside a normal or brisk brachioradialis jerk is reflex spread. The inverted sign needs a reduced brachioradialis response.
• Testing one side only: Without the other arm to compare, a mild asymmetry looks like normal variation.

Inverted supinator sign vs Hoffmann sign: test both, not either

Both are upper motor neuron signs used in myelopathy screening, but you elicit them differently. The Hoffmann sign is often spelled Hoffman’s sign.

To run the Hoffman’s sign test, flick the distal phalanx of the middle finger and watch the thumb and index finger. Flexion shows finger flexor hyperreflexia, but no segmental arc is tested. The inverted supinator test checks the C5-C6 arc and the finger flexors with one tap.

Neither sign proves a level on its own. A positive inverted supinator sign suggests a lesion at or above C5-C6. Across studies, the Hoffmann sign tends to pick up more cases, while the inverted supinator sign is more consistently specific.

A positive Hoffmann sign alone can appear in people with naturally brisk reflexes. When the inverted supinator sign is positive too, a normal variant becomes much harder to argue.

Other upper motor neuron signs complete the picture

No single sign confirms cervical myelopathy. Build a composite picture from several tests, and read them as a cluster.

• Wartenberg thumb sign: The patient flexes their fingers and hooks them against yours. As you pull and they resist, the thumb involuntarily flexes and adducts. That counts as positive.
• Babinski sign: Stroking the sole makes the big toe extend and the other toes fan. It indicates corticospinal (UMN) tract involvement, supporting a central rather than root-level lesion.
• Ankle and patellar clonus: A sudden passive stretch triggers sustained rhythmic beats. Our clonus reflex test guide covers grading and documentation.
• Lower-limb hyperreflexia: Knee and ankle jerks are brisk, and the response spreads beyond the tested segment.
• Lhermitte’s sign: Bending the neck sends an electric shock-like sensation down the spine or into the limbs. Here’s how to run the Lhermitte sign test.

When to refer after a positive inverted supinator test

Refer urgently and arrange a cervical spine MRI when a positive test comes with any of these red flags. Escalate the same day for rapidly progressive deficits or sphincter symptoms.

• Rapidly progressive weakness or sensory loss in the arms or legs
• Upper motor neuron signs on both sides
• Bowel or bladder dysfunction, such as retention, incontinence or urgency
• Gait ataxia or worsening fine motor control, such as writing or buttoning
• A history of significant cervical trauma
• A positive Babinski sign alongside the inverted supinator sign

Without red flags, referral is still needed, for example for isolated hand clumsiness with a stable one-sided sign. Timing then follows your local pathways. Record the functional impact alongside the sign, and review within four to six weeks, or sooner if symptoms progress.

The usual next test is MRI of the cervical spine without contrast. Contrast may be added if a tumor or demyelination is suspected. X-rays and CT show bony narrowing, but they miss changes inside the cord.

Your note should capture the finding and the reasoning behind the referral decision. Our guide to physical therapy compliance covers the record-keeping rules for US and UK practices.

How Pabau keeps serial reflex findings in one patient record

Many physical therapy and chiropractic practices still record neuro exams as free text or on paper. Grades end up in different formats, and the second side often goes unrecorded. Comparing this month’s exam with last month’s then means digging through old notes.

Pabau lets you build customizable assessment forms with fields for each side, the 0-4+ grade and finger flexion. Completed forms save to the patient’s Client record, next to appointments and treatment notes. Our physical therapy EMR brings those records together with scheduling and billing.

The result is a reflex history you can read at a glance. You can also book the six-week recheck before the patient leaves, so the follow-up doesn’t depend on anyone’s memory.

Track reflex findings across every visit

Pabau gives physical therapy and musculoskeletal practices customizable assessment forms and structured client records. Reflex grades, serial findings and referral notes stay in one place for the whole team.

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Conclusion

Make the inverted supinator test part of every exam for neck pain or a clumsy hand. It takes seconds, and a positive result changes what happens next for the patient.

The trade-off is sensitivity. A negative test reassures far less than a positive one should alarm you, so pair it with Hoffmann, Babinski, clonus and gait testing. Grade both sides every time, and write the result down in a form the next clinician can compare.

Consistent notes are what make serial testing worth the effort. Book a demo to see how Pabau’s assessment forms keep reflex grades and referral notes together for your team.

Continue your research

Want a ready-made grading form? Deep tendon reflex exam gives you a template for recording reflex grades on both sides.

Testing for upper motor neuron signs in the hand? Hoffman’s sign test walks through technique, interpretation and referral.

Checking the lower limbs next? Clonus reflex test explains technique, grading and documentation.

Does neck flexion trigger electric shocks? Lhermitte sign test covers how to perform it and act on the findings.

Suspect a nerve root rather than the cord? Spurling’s test covers the procedure, interpretation and clinical accuracy.

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