How to Use a Reflex Hammer and Tuning Fork: A Student's Guide to Neurological Exams

If you are heading into clinical practicals, a reflex hammer and a tuning fork will show up in almost every neurological examination you perform. They look simple, but using them correctly, and interpreting what you find, takes practice. This guide walks through the basics.

The reflex hammer: testing deep tendon reflexes

A reflex hammer tests deep tendon reflexes: the involuntary muscle contraction that happens when a tendon is briefly stretched. This tells you whether the reflex arc, from sensory nerve to spinal cord to motor nerve, is working normally.

The most commonly tested reflexes:

• Biceps reflex: tests the C5 and C6 nerve roots
• Triceps reflex: tests the C7 and C8 nerve roots
• Patellar (knee jerk) reflex: tests the L2 to L4 nerve roots
• Achilles (ankle jerk) reflex: tests the S1 and S2 nerve roots

Technique basics:

1. Make sure the patient, or your practice partner, is relaxed. A tense muscle will blunt or exaggerate the reflex.
2. Locate the tendon by palpation before you strike, so you know exactly where you are aiming.
3. Use a brisk, controlled flick of the wrist, not a stiff-armed swing. The hammer should fall onto the tendon almost under its own weight.
4. Compare left and right sides. Reflexes are graded on a 0 to 4+ scale, where 2+ is normal, 0 is absent and 4+ is a hyperactive response, often with clonus.

A common beginner mistake is striking too hard or too soft. Reflex testing is about consistency between sides, not maximum force.

The tuning fork: vibration sense and hearing

A tuning fork (most commonly 128 Hz for vibration sense and 512 Hz for hearing tests) is used in two different parts of the examination.

Vibration sense

1. Strike the tuning fork gently against your palm to set it vibrating.
2. Place the base of the fork on a bony prominence, commonly the interphalangeal joint of the big toe, the medial malleolus or the wrist.
3. Ask the patient to tell you when they stop feeling the vibration.
4. Compare between limbs, and against your own perception as a control if needed.

Reduced vibration sense that starts in the feet is a classic early sign of peripheral nerve disease.

Hearing tests: Rinne and Weber

• Rinne test: strike the fork and place it on the mastoid process (bone conduction) until the patient stops hearing it, then hold it next to the ear canal (air conduction). Normally air conduction is heard longer than bone conduction. This is a positive Rinne test.
• Weber test: strike the fork and place it on the midline of the forehead or the top of the skull. Ask whether the sound is heard equally in both ears or louder in one. It is interpreted together with the Rinne result.

Together, the Rinne and Weber tests help distinguish conductive from sensorineural hearing loss.

Practice tips for students

• Practise on classmates before your first patient-facing session. The wrist flick takes repetition to get consistent.
• Keep your tuning fork clean and store it away from other metal tools that could nick the tines, since dents affect the vibration.
• Learn the 0 to 4+ grading scale thoroughly. Examiners often ask you to grade a reflex on the spot.

Need the instruments? See the XBONZ reflex hammer, the tuning fork set, or the reflex hammer and tuning fork set.