Deep tendon reflexes, hyperactive
Deep tendon reflexes, hyperactive: Excerpt from Handbook of Signs & Symptoms (Third Edition)
A hyperactive deep tendon reflex (DTR) is an abnormally brisk muscle contraction that occurs in response to a sudden stretch induced by sharply tapping the muscle's tendon of insertion. This elicited sign may be graded as brisk or pathologically hyperactive. Hyperactive DTRs are commonly accompanied by clonus.
The corticospinal tract and other descending tracts govern the reflex arc — the relay cycle that produces any reflex response. A corticospinal lesion above the level of the reflex arc being tested may result in hyperactive DTRs. Abnormal neuromuscular transmission at the end of the reflex arc may also cause hyperactive DTRs. For example, a calcium or magnesium deficiency may cause hyperactive DTRs because these electrolytes regulate neuromuscular excitability. (See Tracing the reflex arc
Although hyperactive DTRs typically accompany other neurologic findings, they usually lack specific diagnostic value. For example, they're an early, cardinal sign of hypocalcemia.
History and physical examination
After eliciting hyperactive DTRs, take the patient's history. Ask about spinal cord injury or other trauma and about prolonged exposure to cold, wind, or water. Could the patient be pregnant? A positive response to any of these questions requires prompt evaluation to rule out life-threatening autonomic hyperreflexia, tetanus, preeclampsia, or hypothermia. Ask about the onset and progression of associated signs and symptoms. Next, perform a neurologic examination. Evaluate the patient's level of consciousness, and test motor and sensory function in the limbs. Ask about paresthesia. Check for ataxia or tremors and for speech and visual deficits. Test for Chvostek's (an abnormal spasm of the facial muscles elicited by light taps on the facial nerve in a patient who has hypocalcemia) and Trousseau's (a carpal spasm induced by inflating a sphygmomanometer cuff on the upper arm to a pressure exceeding systolic blood pressure for 3 minutes in a patient who has hypocalcemia or hypomagnesemia) signs and for carpopedal spasm. Ask about vomiting or altered bladder habits. Make sure to take the patient's vital signs.
Medical causes
Amyotrophic lateral sclerosis (ALS)
ALS produces generalized hyperactive DTRs accompanied by weakness of the hands and forearms and spasticity of the legs. Eventually, the patient develops atrophy of the neck and tongue muscles, fasciculations, weakness of the legs and, possibly, bulbar signs (dysphagia, dysphonia, facial weakness, and dyspnea).
Brain tumor.
A cerebral tumor causes hyperactive DTRs on the side opposite the lesion. Associated signs and symptoms develop slowly and may include unilateral paresis or paralysis, anesthesia, visual field deficits, spasticity, and a positive Babinski's reflex.
Hypocalcemia
Hypocalcemia may produce a sudden or gradual onset of generalized hyperactive DTRs with paresthesia, muscle twitching and cramping, positive Chvostek's and Trousseau's signs, carpopedal spasm, and tetany.
Hypomagnesemia
Hypomagnesemia results in the gradual onset of generalized hyperactive DTRs accompanied by muscle cramps, hypotension, tachycardia, paresthesia, ataxia, tetany and, possibly, seizures.
Hypothermia
Mild hypothermia (90 to 94 F [32.2 to 34.4 C]) produces generalized hyperactive DTRs. Other signs and symptoms include shivering, fatigue, weakness, lethargy, slurred speech, ataxia, muscle stiffness, tachycardia, diuresis, bradypnea, hypotension, and cold, pale skin.
Preeclampsia.
Occurring in pregnancy of at least 20 weeks' gestation, preeclampsia may cause a gradual onset of generalized hyperactive DTRs. Accompanying signs and symptoms include increased blood pressure; abnormal weight gain; edema of the face, fingers, and abdomen after bed rest; albuminuria; oliguria; a severe headache; blurred or double vision; epigastric pain; nausea and vomiting; irritability; cyanosis; shortness of breath; and crackles. If preeclampsia progresses to eclampsia, the patient develops seizures.
Spinal cord lesion
Incomplete spinal cord lesions cause hyperactive DTRs below the level of the lesion. In a traumatic lesion, hyperactive DTRs follow resolution of spinal shock. In a neoplastic lesion, hyperactive DTRs gradually replace normal DTRs. Other signs and symptoms are paralysis and sensory loss below the level of the lesion, urine retention and overflow incontinence, and alternating constipation and diarrhea. A lesion above T6 may also produce autonomic hyperreflexia with diaphoresis and flushing above the level of the lesion, a headache, nasal congestion, nausea, increased blood pressure, and bradycardia.
Stroke.
A stroke that affects the origin of the corticospinal tracts causes the sudden onset of hyperactive DTRs on the side opposite the lesion. The patient may also have unilateral paresis or paralysis, anesthesia, visual field deficits, spasticity, and a positive Babinski's reflex.
Tetanus.
With tetanus, the sudden onset of generalized hyperactive DTRs accompanies tachycardia, diaphoresis, a low-grade fever, painful and involuntary muscle contractions, trismus (lockjaw), and risus sardonicus (a masklike grin).
Special considerations
Prepare the patient for diagnostic tests to evaluate hyperactive DTRs. These may include laboratory tests for serum calcium, magnesium, and ammonia levels; spinal X-rays; magnetic resonance imaging; a computed tomography scan; lumbar puncture; and myelography.
If motor weakness accompanies hyperactive DTRs, perform or encourage range-of-motion exercises to preserve muscle integrity and prevent deep vein thrombosis. Also, reposition the patient frequently, provide a special mattress, massage his back, and ensure adequate nutrition to prevent skin breakdown. Administer a muscle relaxant and sedative to relieve severe muscle contractions. Keep emergency resuscitation equipment on hand. Provide a quiet, calm atmosphere to decrease neuromuscular excitability. Assist with activities of daily living, and provide emotional support.
Pediatric pointers
Hyperreflexia may be a normal sign in neonates. After age 6, reflex responses are similar to those of adults. When testing DTRs in small children, use distraction techniques to promote reliable results.
Cerebral palsy commonly causes hyperactive DTRs in children. Reye's syndrome causes generalized hyperactive DTRs in stage II; in stage V, DTRs are absent. Adult causes of hyperactive DTRs may also appear in children.
Pictures
Book Source Details
- Book Title: Handbook of Signs & Symptoms (Third Edition)
- Author(s): Springhouse
- Year of Publication: 2006
- Copyright Details: Handbook of Signs & Symptoms (Third Edition), Copyright © 2006 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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