How to guage Clonus

After completing the neurological assessment and examining the patient’s deep tendon reflexes, if the reflexes appear hyperactive, take a moment to ascertain for clonus. Clonus is an abnormal movement characterised by rhythmic alternating muscle contraction and leisure occurring in quick succession, attributable to stretching of the tendon (Gelb, 2022; Hinkle, 2021).

Clonus is a marker of hyperreflexia and will be related to changes in upper motor neurons (Zimmerman and Hubbard, 2022). This is normally accompanied by other upper motor neuron symptoms, including spasticity and weakness.

Clonus Test (Bickley et al., 2021)

To test for ankle clonus or Achilles tendon, start by supporting the knee in a partially flexed position. With the opposite hand, dorsiflex and plantar flex the foot several times and ask the patient to chill out. Then firmly dorsiflex your foot and keep it dorsiflexed. Observe the rhythmic oscillations between dorsiflexion and plantar flexion. The ankle shouldn’t react to this movement and will remain dorsiflexed. If the patient is tense or has just exercised, several myoclonus may occur. However, persistent clonus indicates a central nervous system (CNS) disease affecting the corticospinal tract. For a reflex to be grade 4, clonus should be present. Some physicians will use grade 5 to define persistent clonus and grade 4 for non-persistent clonus that eventually resolves after 2-10 beats (Gelb, 2022). Other joints might be examined for clonus. For example, a pointy downward movement of the patella could cause patellar clonus in an prolonged knee. You also can use your jaw, wrist joint, biceps and triceps.

Clonus – an indication of several disorders

Clonus can signal disorders akin to stroke, encephalopathy, cerebral palsy, multiple sclerosis, and spinal cord injury. It is usually used as a test for suspected serotonin syndrome, which could also be attributable to psychiatric medications including monoamine oxidase inhibitors, selective serotonin reuptake inhibitors, serotonin and norepinephrine reuptake inhibitors, tricyclic antidepressants, or street drugs akin to cocaine, ecstasy, and amphetamine. Clonus might also predict seizures in patients who’ve overdosed on the serotonin norepinephrine reuptake inhibitor (SNRI) tramadol (Zimmerman and Hubbard, 2022).

Testing for clonus is effective and efficient and might be performed without special equipment. If clonus is observed, the patient needs to be referred to a neurologist for further evaluation.

Bickley, L. S., Szilagyi, P. G., Hoffman, R. M., & Soriano, R. P. (2021). Bate’s guide to physical examination and interviewing (thirteenth ed.). Wolters Kluwer Health: Philadelphia.

Gelb, D. (2022, July 1). Detailed neurological examination in adults. . https://www.uptodate.com/contents/the-detailed-neurologic-examination-in-adults

Hinkle, J. (2021). Brunner and Suddarth’s textbook of medical-surgical nursing (fifteenth edition)^vol ed.). Wolters Kluwer Health. https://wolterskluwer.vitalsource.com/books/9781975161057

Zimmerman, B., & Hubbard, J. B. (2022, June 24). Clone. https://www.ncbi.nlm.nih.gov/books/NBK534862/