Deep tendon reflexes, hypoactive
Deep tendon reflexes, hypoactive: Excerpt from Signs & Symptoms: A 2-in-1 Reference for Nurses
Hypoactive deep tendon reflexes (DTRs) are abnormally diminished muscle contractions that occur in response to a sudden stretch induced by sharply tapping the muscle’s tendon of insertion. Symmetrically reduced reflexes may be normal.
Normally, DTRs depend on intact receptors, intact sensory-motor nerve fibers, intact neuromuscular-glandular junctions, and functional synapses in the spinal cord. Hypoactive DTRs may result from damage to the reflex arc involving the specific muscle, the peripheral nerve, the nerve roots, or the spinal cord at that level. Hypoactive DTRs are an important sign of many disorders, especially when they appear with other neurologic signs and symptoms. (See Documenting deep tendon reflexes.)
History
After eliciting hypoactive DTRs, obtain a thorough history from the patient or a family member. Have him describe current signs and symptoms in detail. Then take a family and drug history.
Physical assessment
Evaluate the patient’s level of consciousness. Test motor function in his limbs, and palpate for muscle atrophy or increased mass. Test sensory function, including pain, touch, temperature, and vibration sense. Evaluate paresthesia. To observe gait and coordination, have the patient take several steps. To check for Romberg’s sign, ask him to stand with his feet together and his eyes closed. During conversation, evaluate speech. Check for signs of vision and hearing loss. Abrupt onset of hypoactive DTRs accompanied by muscle weakness may occur with life-threatening Guillain-Barré syndrome, botulism, or spinal cord lesions with spinal shock.
Look for autonomic nervous system effects by taking vital signs and monitoring for increased heart rate and blood pressure. Also, inspect the skin for pallor, dryness, flushing, and diaphoresis. Auscultate for hypoactive bowel sounds, and palpate for bladder distention. Ask about nausea, vomiting, constipation, and incontinence.
Medical causes
Botulism
With botulism, generalized hypoactive DTRs accompany progressive descending muscle weakness. Initially, the patient usually complains of blurred and double vision and, occasionally, of anorexia, nausea, and vomiting. Other early bulbar findings include vertigo, hearing loss, dysarthria, and dysphagia. The patient may have signs of respiratory distress and severe constipation marked by hypoactive bowel sounds.
Cerebellar dysfunction
Cerebellar dysfunction may produce hypoactive DTRs by increasing the level of inhibition through long tracts upon spinal motor neurons. Associated clinical findings vary depending on the cause and location of the dysfunction.
Guillain-Barré syndrome
Guillain-Barré syndrome causes bilateral hypoactive DTRs that progress rapidly from hypotonia to areflexia in several days. Guillain-Barré syndrome typically causes muscle weakness that begins in the legs and then extends to the arms and, possibly, to the trunk and neck muscles. Occasionally, weakness may progress to total paralysis. Other signs and symptoms include cranial nerve palsies, pain, paresthesia, and signs of brief autonomic dysfunction, such as sinus tachycardia or bradycardia, flushing, fluctuating blood pressure, and anhidrosis or episodic diaphoresis.
Usually, muscle weakness and hypoactive DTRs peak in severity within 10 to 14 days; then symptoms begin to clear. However, in severe cases, residual hypoactive DTRs and motor weakness may persist.
Peripheral neuropathy
Characteristic of end-stage diabetes mellitus, renal failure, alcoholism, and an adverse effect of various medications, peripheral neuropathy results in progressive hypoactive DTRs. Other effects include motor weakness, sensory loss, paresthesia, tremors, and possible autonomic dysfunction, such as orthostatic hypotension and incontinence.
Polymyositis
With polymyositis, hypoactive DTRs accompany muscle weakness, pain, stiffness, spasms and, possibly, increased size or atrophy. These effects are usually temporary; their location varies with the affected muscles.
Spinal cord lesions
Spinal cord injury or complete transection produces spinal shock, resulting in hypoactive DTRs (areflexia) below the level of the lesion. Associated signs and symptoms include quadriplegia or paraplegia, flaccidity, loss of sensation below the level of the lesion, and dry, pale skin. Also characteristic are urine retention with overflow incontinence, hypoactive bowel sounds, constipation, and genital reflex loss. Hypoactive DTRs and flaccidity are usually transient; reflex activity may return within several weeks.
Syringomyelia
Permanent bilateral hypoactive DTRs occur early in syringomyelia, a slowly progressive disorder. Other signs and symptoms of syringomyelia are muscle weakness and atrophy; loss of sensation, usually extending in a capelike fashion over the arms, shoulders, neck, back, and occasionally the legs; deep, boring pain (despite analgesia) in the limbs; and signs of brain stem involvement (nystagmus, facial numbness, unilateral vocal cord paralysis or weakness, and unilateral tongue atrophy).
Other causes
Drugs
Barbiturates and paralyzing drugs, such as pancuronium and curare, may cause hypoactive DTRs.
Special considerations
If the patient has sensory deficits, protect him from injury caused by heat, cold, or pressure. Test his bath water, and reposition him frequently, ensuring a soft, smooth bed surface. Keep his skin clean and dry to prevent breakdown. Perform or encourage range-of-motion exercises. Also encourage a balanced diet with plenty of protein and adequate hydration.
Pediatric pointers
Hypoactive DTRs commonly occur in patients with muscular dystrophy, Friedreich’s ataxia, syringomyelia, and spinal cord injury. They also accompany progressive muscular atrophy, which affects preschoolers and adolescents.
Use distraction techniques to test DTRs; assess motor function by watching the infant or child at play.
Geriatric pointers
Elderly patients may have reduced DTRs because of a decrease in the number of nerve axons and demyelination of axons. The Achilles tendon reflex may be difficult to elicit in these patients.
Patient counseling
Encourage the patient to perform activities of daily living as independently as possible. Assist the patient when necessary. Try to strike a balance between promoting independence and ensuring the patient’s safety. Encourage him to walk with assistance. Make sure personal care articles are within easy reach, and provide an obstacle-free course from his bed to the bathroom.
Pictures
Book Source Details
- Book Title: Signs & Symptoms: A 2-in-1 Reference for Nurses
- Author(s): Springhouse
- Year of Publication: 2007
- Copyright Details: Signs & Symptoms: A 2-in-1 Reference for Nurses, Copyright © 2007 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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