Reflex Testing

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There are three types of reflexes

1. Muscle stretch reflexes: myotatic and inverse myotatic
2. Cutaneous reflexes
3. Primitive reflexes

The reflexes commonly tested during a clinical examination are elicited by a brisk stretch applied to a muscle, leading to the activation of muscle spindles. These are often referred to as deep tendon reflexes, although this term is a misnomer as the primary stimulus is muscle spindle stretch, not tendon organ activation. The Golgi tendon organs, located within tendons, have an opposing effect, causing muscle relaxation via the inverse myotatic reflex. This reflex is generally not tested directly during routine examination but occurs as a protective mechanism with sudden, extreme stretch to a tendon.

Muscle Stretch Reflexes

Grading

NINDS Muscle Stretch Reflex Scale

Grade	Finding
0	Reflex absent despite reinforcement
1	Reflex small, less than normal; includes a trace response or a response brought out only with reinforcement
2	Reflex in lower half of normal range
3	Reflex in upper half of normal range
4	Reflex enhanced, more than normal; includes clonus if present, which optionally can be noted in an added verbal description of the reflex

Reflexes can be reinforced using the Jendrassik manoeuvre (e.g., asking the patient to hook together the flexed fingers of both hands and pull them apart strongly, or to clench their teeth) while eliciting the reflex. This is crucial before classifying a reflex as absent. This manoeuvre can also be helpful in distracting patients who are struggling to relax.

Clonus

Clonus is a series of involuntary, rhythmic, muscular contractions and relaxations. It is a strong sign of an upper motor neuron lesion and is often associated with hyperreflexia (Grade 4 reflexes).

• Testing for Ankle Clonus: Support the patient's knee in a partially flexed position. Briskly and firmly dorsiflex the patient's foot, then maintain light pressure. Sustained clonus (typically more than 3-5 beats) of rhythmic plantarflexion/dorsiflexion is considered pathological.
• Testing for Patellar Clonus: With the patient supine and the leg extended and relaxed, briskly and sharply push the patella distally. Rhythmic superior and inferior movements of the patella indicate clonus.

Clinical Significance

Deep tendon reflex testing for radiculopathy generally demonstrates high specificity but often low to moderate sensitivity. This means an abnormal reflex (diminished or absent) is a strong indicator that radiculopathy might be present, but a normal reflex does not effectively rule it out.

Disease at different locations in the nervous system causes different findings

• Disease at peripheral nerve or spinal segment (nerve root): Reduced or abolished reflex (lower motor neuron [LMN] response).
• Disease along the descending corticospinal pathway (brain or spinal cord): Exaggerated reflex (upper motor neuron [UMN] response).
• Disease of the spinal cord: Abolishes the reflex at the level of the lesion (LMN response due to damage to the reflex arc itself), and exaggerates all reflexes from spinal levels below the level of the lesion (UMN response due to interruption of descending inhibitory pathways).

Absent or exaggerated reflexes are only relevant when one of the following is true

1. The absent reflex is present along with other lower motor neuron signs such as weakness, atrophy, fasciculations.
2. The exaggerated reflex is present along with other upper motor neuron signs such as weakness, spasticity, Babinski or Hoffman sign. (see video on Hoffmans sign)
3. The reflexes are asymmetric which either means that the side with the reduced reflex amplitude has a lower motor neuron lesion or the side with the higher amplitude has an upper motor neuron lesion.
4. The exaggerated reflex is unusually brisk compared to a more proximal spinal segmental level reflex. This suggests spinal cord disease between the two segments.

Also look for "overflow." This is when there is spread of the reflex from one root level to another. For example, when testing the biceps reflex and there is both elbow flexion (expected C5, C6) and wrist extension or finger movement (overflow, signifying added C6, C7, C8 efferent signal spread). This is a sign of hyperreflexia and UMN pathology.

Diagnostic Utility in Radiculopathies

Absent or diminished reflexes have localizing value in radiculopathies. These must be interpreted within a comprehensive clinical framework, considering history, sensory testing, motor strength, and provocative maneuvers, as isolated reflex abnormalities have limited diagnostic power. The diagnostic significance is heightened by asymmetry.

Localising Value of Diminished Reflexes in Radiculopathies

Radiculopathy	Absent Reflex	+LR for any root level	+LR for representative level
C5-C6	Biceps	10	1.4 - 4.9
C5, C6, C7	Brachioradialis	8	1.2 - 2.83
C7	Triceps	2	0.4 - 1.75
L3 or L4	Quadriceps	42.5	6.21 for L3/4 herniation†
L5	Medial Hamstring	18	5.16 for L4/5 herniation†
S1	Achilles	6	4.33 for L5/S1 herniation†
†LRs calculated from figures provided in study.

The pectoralis reflex may be increased in cervical myelopathy above the C4 level.

Full Reflex Chart

Upper Extremity Reflexes

Reflex	Nerve Root	Efferent Limb	Reflex Test	Look for
Jaw Jerk (Masseter)	CN V	CN V (Trigeminal)	1. Patient's mouth slightly open and jaw relaxed. 2. Examiner places thumb or finger on patient's chin and taps it gently with reflex hammer.	Closure of the jaw (masseter muscle contraction).
Biceps	C5, C6	Musculocutaneous	1. Patient relaxes upper limb at side, resting hand on lap if seated. 2. Examiner places one finger over the biceps tendon, then strikes her own finger with the reflex hammer.	Elbow flexion or biceps activation.
Brachioradialis	C6	Radial	1. Patient allows upper limb to rest on the lap with elbow in moderate flexion. 2. Examiner taps the brachioradialis tendon where it crosses the radius at approximately the distal third of the forearm.	Brachioradialis activation during elbow flexion.
Extensor Carpi Radialis	C5-C7	Radial	1. Patient relaxes arm on table or lap, with the palm down. 2. Examiner taps over the extensor carpi radialis tendon at the lateral proximal forearm, just distal to the lateral epicondyle.	Wrist extension.
Pronator Teres	C6-C7	Median	1. Patient sits with elbow in moderate flexion and forearm in neutral (thumb up). 2. Examiner taps the distal radius about one-third of the distance from wrist to elbow.	Forearm pronation or twitch along pronator teres.
Triceps	C7	Radial	1. Examiner lifts patient’s arm into abduction, allowing elbow to flex and forearm to swing freely. 2. Examiner taps triceps tendon just proximal to olecranon.	Elbow extension.
Finger Flexors	C8-T1	Median (index/middle), Ulnar (ring/little)	1. Patient rests forearm with palm up. 2. Examiner places her fingers against patient’s fingers at PIP joints and asks for gentle finger flexion. 3. Examiner taps dorsal side of her own fingers.	Finger flexion.

Lower Extremity Reflexes

Reflex	Nerve Root	Peripheral Nerve	Reflex Test	Look for
Adductor	L2, L3, L4	Obturator	1. Patient supine or seated with legs hanging. 2. Examiner taps adductor tendons on medial distal thigh.	Hip adduction.✡︎
Patellar	(L2), L3 - L4	Femoral	1. Patient seated, knees flexed and hanging freely. 2. Examiner taps patellar tendon below patella.	Quadriceps contraction, knee extension.
Medial Hamstring	L5	Tibial	1. Patient seated, foot supported. 2. Examiner strikes finger placed over semitendinosus/semitendinosus tendon.	Knee flexion or tendon tensing.
Ankle Jerk	S1, (S2)	Tibial	1. Patient seated, feet flat. 2. Examiner taps Achilles tendon.	Heel rise/plantarflexion.
Lateral Hamstring	S1, S2	S1, S2, Tibial and Peroneal	1. Patient seated, foot supported. 2. Examiner strikes finger over biceps femoris tendon.	Knee flexion or tendon tensing.
✡︎The crossed adductor response describes adduction of the contralateral hip when the patellar or adductor tendons are tapped on the opposite side. It is an example of overflow of reflexes and is usually indicative of upper motor neuron pathology.

Cutaneous Reflexes

Superficial Abdominal Reflex

The superficial abdominal reflex tests T6-T11. The skin of the abdomen is stroked which causes the underlying abdominal wall muscle to contract. One abdominal quadrant is tested at a time. The skin can be stroked lateral to medial or medial to lateral.

This reflex is reduced in both upper and lower motor neuron disease, however they are absent in 20% of normal patients and in the elderly. it is also common to have asymmetric reflexes or reflexes only preserved in the upper quadrants in normal individuals.

Bulvocavernosus Reflex

In lithotomy, apply sudden manual compression to the glans penis or clitoris, feeling for reflex contraction of the bulbocavernosus muscle and external anal sphincter. The reflex contraction is felt by palpating the skin behind the scrotum or per rectum. Percussing the suprapubic area or pulling the balloon of an inflated Foley catheter can also cause the reflex.

This reflex tests the conus medullaris and the S2-4 spinal nerves. Its absence has a +LR in women of 2.7, and +LR in men of 13.

Pathological Reflexes

Babinski Reflex

The Babinski reflex (also known as the Babinski sign or upgoing toe) is an abnormal cutaneous reflex indicative of UMN disease affecting the corticospinal tract. It is characterized by the upward movement (extension or dorsiflexion) of the great toe when the lateral aspect of the sole of the foot is stroked, from the heel towards the base of the toes, and then medially across the metatarsal heads. This reflex is a primitive flexion response normally present in infants up to about one or two years old; its persistence or re-emergence in later life signifies damage to the pyramidal tracts. While the term "extensor response" is sometimes used for the upgoing toe, this can be confusing as physiologists refer to this upward movement as part of a broader flexion withdrawal response of the limb.

The key indicator of a pathological upgoing toe is the contraction of the extensor hallucis longus muscle, visible as its tendon becoming conspicuous on top of the great toe; mere movement of the toe can be misleading due to joint disease or other foot movements like ankle dorsiflexion or the toe returning from an initial downward flex. It's also important to note that over 90% of individuals with a true pathological upgoing toe will also exhibit weakness or impaired fine motor skills in that foot, which can be tested by tasks like rapid foot tapping. Furthermore, a pathological upgoing toe is typically reproducible and occurs in conjunction with a broader flexion response in the entire limb, observable in the ipsilateral tensor fascia lata and hamstring muscles. Fanning of the toes is a normal phenomenon and not part of the pathological sign. For ticklish patients where withdrawal makes interpretation difficult, allowing them to stroke their own sole can sometimes reduce this reaction and reveal a clearer response.

In patients presenting with neck or arm pain indicative of cervical spine disease, a positive Babinski response is a strong indicator of significant cervical myelopathy. Its presence markedly increases the likelihood of detecting myelopathy on a cervical MRI, with a very high positive likelihood ratio but a low sensitivity. In diagnosing myelopathy in patients with neck pain, the Babinski response has been found to be a more accurate indicator than other reflexes such as the inverted supinator reflex or abnormal finger flexion reflexes.

Hoffman Sign

The Hoffmann sign is another well-established neurological reflex test used to detect cervical myelopathy. It is performed by supporting the patient's relaxed hand with fingers partially flexed and stabilising the finger at the distal PIP. The examiner then firmly flicking the distal phalanx downwards. positive sign is indicated by involuntary flexion of the neighboring fingers and thumb

Trömner Sign

The Trömner sign is as an alternative to the Hoffmann sign for detecting cervical myelopathy. It is done almost the same way as Hoffman but the opposite direction. Stabilise the distal PIP, but instead of flicking downwards the examiner flicks the distal phalanx upwards from the volar surface. A positive response is defined similarly to the Hoffmann sign, with involuntary flexion of the patient's index finger and thumb. This sign has been found to have a higher sensitivity (94%) than Hoffman and the inverted radial reflex (both 76%) in detecting CSM, even in mild cases, and its relatively high negative predictive value (85%), making it useful for ruling out CSM. Furthermore, the research found a high incidence of positive Trömner signs in patients with presymptomatic cervical cord compression.

Inverted Radial Reflex (Inverted Supinator Reflex)

The Inverted Radial Reflex is a pathological sign indicative of a spinal cord lesion at the C5 or C6 level. The test is performed in the same manner as eliciting the brachioradialis reflex: the examiner taps the distal brachioradialis tendon at the styloid process of the radius or slightly more proximally. A normal Response (Brachioradialis Reflex) is Elbow flexion and/or forearm supination. A pathological Response (Inverted Radial Reflex) is where instead of, or in addition to, the normal brachioradialis contraction, there is flexion of the fingers and sometimes extension of the elbow. The absence of elbow flexion/supination with presence of finger flexion is most characteristic..

See Also

• Motor System Examination
• Skeletal Muscle
• Radicular Pain and Radiculopathy
• Lumbar Radicular Pain
• Cervical Radicular Pain