Ankle jerk reflex
Physiological stretch reflex
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Related on Lably
Through Anatomical terms of motion, Reflex arc and Spinal cord
Root value
This reflex is mediated by the S1 spinal segment of the spinal cord.
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Procedure and components
Ankle of the patient is relaxed. It is helpful to support the ball of the foot at least somewhat to put some tension in the Achilles tendon, but don’t completely dorsiflex the ankle. A small strike is given on the Achilles tendon using a rubber hammer to elicit the response. If the practitioner is not able to elicit a response, a Jendrassik maneuver can be tried by having the patient cup their fingers on each hand and try to pull the hands apart. A positive response is marked by a brisk plantarflexion of the foot. The response is also graded into Grade 0-4 according to the reflex grading system.
Absent ankle jerk
The Achilles reflex checks if the S1 and S2 nerve roots are intact and could be indicative of sciatic nerve pathology. It is classically delayed in hypothyroidism. This reflex is usually absent in disk herniations at the L5—S1 level. A reduction in the ankle jerk reflex may also be indicative of peripheral neuropathy.
Common causes
- Lumbar herniated disk syndrome
- Lumbar spinal stenosis
- Endocrine disorders
- Sciatic neuropathy
- Lumbosacral plexus disorder
- Amyotrophic lateral sclerosis
- Cauda equina syndrome
- Lumbar radiculopathy
- Holmes-Adie syndrome
- Idiopathic
- Trauma
- Hypothermia
- Infectious diseases
- Tabes dorsalis
- Poliomyelitis, acute
- Lumbar disk infection/pyogenic
- Arachnoiditis lumbosacral
- Neoplastic disorders
- Primary
- Secondary
- Allergic, collagen, autoimmune diseases
- Diabetic neuropathy
Rarer causes
- Abetalipoproteinemia
- Electrolyte abnormalities
- Deficiency disorders
- Vitamin E deficiency
- Congenital developmental disorders
- Genetic disorders
- Hypokalemic periodic paralysis
- Charcot–Marie–Tooth disease
- Spinal muscular atrophy
- Friedreich's ataxia
- Drugs
- Tubocurarine
- Pyridoxine excess/megadose
- Chronic alcoholism
Ankle clonus
Grade 4 ankle hyperreflexia is called ankle clonus. There is repetitive ankle dorsiflexion and plantarflexion on passive dorsiflexion of the foot by the examiner till the force applied by the examiner is withdrawn.
Causes
Any spinal cord lesions, be it traumatic, neoplastic, pyogenic, vascular above the level of S1 can cause clonus. This is because of the spasticity caused by the UMN type of injury causing hyperreflexia and clonus. Some other causes of clonus are