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ULY CLINIC

ULY CLINIC

6 Julai 2025, 09:36:33

Hypoactive deep tendon reflex

Hypoactive deep tendon reflex
Hypoactive deep tendon reflex
Hypoactive deep tendon reflex

A hypoactive deep tendon reflex (DTR) is a diminished or absent muscle response to tendon tapping. It may be graded as diminished (+) or absent (0). While symmetrical hypoactivity can be normal, asymmetrical or sudden-onset hypoactive DTRs are often pathological and indicate lower motor neuron or reflex arc disruption.


Understanding the Reflex Arc

Hypoactive DTRs suggest a problem within the reflex arc, including:

  • Afferent (sensory) nerve fibers

  • Spinal cord segment at the level of the reflex

  • Efferent (motor) nerve fibers

  • Neuromuscular junction

  • Target muscle

They often point to lower motor neuron (LMN) pathology, as opposed to upper motor neuron (UMN) lesions, which cause hyperreflexia.


History and Physical examination

After identifying hypoactive DTRs, assess:

  • History: Weakness, sensory loss, trauma, toxin exposure, infections, autoimmune conditions.

  • Medication use: Sedatives, muscle relaxants, neurotoxic drugs.

  • Neurologic exam: Evaluate tone, coordination, muscle bulk, and strength.

  • Gait and balance: Romberg’s test and heel-to-shin or finger-to-nose maneuvers.

  • Autonomic features: Look for bradycardia, bowel or bladder dysfunction.


Medical causes

Table: Causes of hypoactive deep tendon reflexes

Cause

Clinical Features

Special Considerations

Guillain-Barré Syndrome (GBS)

Rapidly progressive ascending weakness, areflexia, paresthesia, autonomic dysfunction (e.g., fluctuating BP, tachycardia)

Medical emergency; monitor respiratory function and cardiac rhythm; IVIG or plasmapheresis required

Botulism

Descending flaccid paralysis, blurred vision, diplopia, dysphagia, constipation, hypoactive bowel sounds

Notify public health; monitor for respiratory failure; antitoxin may be indicated

Eaton-Lambert Syndrome

Proximal muscle weakness that improves with activity, hypoactive reflexes, autonomic symptoms

Often associated with small-cell lung carcinoma; EMG diagnostic; may respond to 3,4-DAP and cancer treatment

Peripheral Neuropathy (e.g., diabetic, alcoholic)

Distal weakness, sensory loss (glove and stocking), paresthesia, hypoactive ankle reflexes

Tight glucose control (if diabetic); vitamin B1/B12 supplementation; fall risk assessment

Polymyositis

Proximal muscle weakness, pain, stiffness, hypoactive or normal reflexes, elevated CK

Consider autoimmune screen; physical therapy and corticosteroids are mainstay

Spinal Cord Lesions (acute phase)

Flaccid paralysis, areflexia below lesion, urinary retention, sensory loss, hypotension

Reflexes may return after spinal shock; neuroimaging essential; bladder/bowel care required

Syringomyelia

Cape-like sensory loss (pain and temperature), hand muscle atrophy, areflexia in upper limbs

MRI diagnostic; may require surgical decompression; monitor for progression

Friedreich’s Ataxia

Progressive ataxia, areflexia (esp. lower limbs), dysarthria, cardiomyopathy

Genetic testing confirms; multisystem involvement; supportive care for ataxia and cardiac issues

Hypothyroidism

Fatigue, weight gain, cold intolerance, delayed reflexes, puffy face, bradycardia

Treat with levothyroxine; monitor reflex recovery over time

Hypokalemia

Muscle cramps, weakness, arrhythmias, constipation, diminished reflexes

ECG monitoring; replace potassium; identify underlying cause (e.g., diuretics)

Barbiturates & Sedatives

CNS depression, slurred speech, drowsiness, hyporeflexia

Monitor airway and consciousness; supportive care; consider antidotes if available

Myasthenia Gravis

Fluctuating weakness, ptosis, diplopia; reflexes usually normal, may be diminished with disuse

Test for AChR antibodies; treat with pyridostigmine and immunosuppression

Uremic Neuropathy

Burning feet, reduced vibration sense, distal weakness, hypoactive DTRs

Improve dialysis adequacy; symptom relief with gabapentinoids or tricyclics

Spinal Muscular Atrophy (Pediatric)

Progressive weakness, absent reflexes, fasciculations (esp. tongue), hypotonia

Genetic diagnosis; supportive care, new therapies (e.g., nusinersen) may slow progression

Muscular Dystrophy (Pediatric)

Gower’s sign, calf pseudohypertrophy, absent reflexes in later stages

Genetic counseling; monitor cardiac/respiratory status; steroids may slow progression


Special considerations

  • Supportive care: Encourage movement, maintain muscle integrity through range-of-motion exercises, and prevent complications like DVT or pressure ulcers.

  • Safety: Provide assistive devices to reduce fall risk, ensure obstacle-free paths, and protect areas with sensory loss from burns or pressure injury.

  • Nutrition and hydration: Essential to support neuromuscular function.

  • Temperature and skin care: Regularly assess skin integrity and avoid extreme temperatures.

  • Psychosocial support: Educate caregivers and patients about adaptation strategies, especially in chronic or progressive conditions.


Pediatric consideration

  • Normal in infants; must be interpreted with developmental milestones.

  • Common in muscular dystrophy, spinal muscular atrophy, Friedreich’s ataxia, and syringomyelia.

  • Use distraction techniques to obtain accurate results in young children.


References
  1. Born-Frontsberg E, Reincke M, Rump LC, Hahner S, Diederich S, Lorenz R, et al. Cardiovascular and cerebrovascular comorbidities of hypokalemic and normokalemic primary aldosteronism: Results of the German Conn’s Registry. J Clin Endocrinol Metab. 2009;94(4):1125–30.

  2. Krantz MJ, Martin J, Stimmel B, Mehta D, Haigney MC. QTc interval screening in methadone treatment. Ann Intern Med. 2009;150:387–95.

  3. Aminoff MJ, Greenberg DA, Simon RP. Clinical Neurology. 10th ed. New York: McGraw-Hill Education; 2019.

  4. Longo DL, Fauci AS, Kasper DL, Hauser SL, Jameson JL, Loscalzo J. Harrison’s Principles of Internal Medicine. 20th ed. New York: McGraw-Hill Education; 2018.

  5. McCance KL, Huether SE. Pathophysiology: The Biologic Basis for Disease in Adults and Children. 8th ed. St. Louis: Elsevier; 2019.

  6. Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, editors. Nelson Textbook of Pediatrics. 21st ed. Philadelphia: Elsevier; 2020.

  7. Darras BT, Jones HR, Ryan MM, De Vivo DC. Neuromuscular Disorders of Infancy, Childhood, and Adolescence: A Clinician's Approach. 2nd ed. London: Elsevier; 2015.

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