Professional Guide to Signs and Symptoms
5th Edition

Deep tendon reflexes, hypoactive
A hypoactive deep tendon reflex (DTR) is an abnormally diminished muscle contraction
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that occurs in response to a sudden stretch induced by sharply tapping the muscle’s tendon of insertion. It may be graded as minimal (+) or absent (0). Symmetrically reduced (+) reflexes may be normal.
Normally, a DTR depends on an intact receptor, intact sensory-motor nerve fiber, an intact neuromuscular-glandular junction, and a functional synapse 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 AND PHYSICAL EXAMINATION
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.
Next, 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 sensation. Ask about 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 his speech. Check for signs of vision or hearing loss. Abrupt onset of hypoactive DTRs accompanied by muscle weakness may occur in 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, or diaphoresis. Auscultate for hypoactive bowel sounds, and palpate for bladder distention. Ask about nausea, vomiting, constipation, and incontinence.
MEDICAL CAUSES
  • Botulism. In this disorder, generalized hypoactive DTRs accompany progressive
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    descending muscle weakness. Initially, the patient usually complains of blurred and double vision and, occasionally, 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. This disorder 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.
  • Eaton-Lambert syndrome. This disorder produces generalized hypoactive DTRs. Early signs include difficulty rising from a chair, climbing stairs, and walking. The patient may complain of achiness, paresthesia, and muscle weakness that’s most severe in the morning. Weakness improves with mild exercise and worsens with strenuous exercise.
  • Guillain-Barré syndrome. This disorder causes bilateral hypoactive DTRs that progress 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, and alcoholism, and as an adverse effect of various medications, peripheral neuropathy results in progressive hypoactive DTRs. Other effects include motor weakness, sensory loss, paresthesia, tremors and, possibly, signs of autonomic dysfunction, such as orthostatic hypotension and incontinence.
  • Polymyositis. In this disorder, 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 this slowly progressive disorder. Other signs and symptoms 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). Syringomyelia is more common in males than in females.
  • Tabes dorsalis. This progressive disorder results in bilateral hypoactive DTRs in the legs and occasionally the arms. Associated signs and symptoms include sharp pain and paresthesia of the legs, face, or trunk; visceral pain with retching and vomiting; sensory loss in the legs; ataxic gait with a positive Romberg’s sign; urine retention and urinary incontinence; and arthropathies.
OTHER CAUSES
  • Drugs. Barbiturates and paralyzing drugs, such as pancuronium, may cause hypoactive DTRs.
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SPECIAL CONSIDERATIONS
Help the patient perform his daily activities. Try to strike a balance between promoting independence and ensuring his 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.
If the patient has sensory deficits, protect him from injury from 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 children with muscular dystrophy, Friedreich’s ataxia, syringomyelia, or a 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.