Decreased Deep Tendon Reflexes and Dysautonomia
Decreased deep tendon reflexes are NOT a typical or defining sign of dysautonomia, though they may occasionally coexist when peripheral neuropathy affects both somatic and autonomic nerve fibers.
Understanding the Relationship
Dysautonomia primarily affects the autonomic nervous system (controlling involuntary functions like blood pressure, heart rate, and temperature regulation), while deep tendon reflexes are mediated by somatic motor and sensory pathways 1. These are fundamentally different neurological systems.
When Decreased Reflexes May Accompany Dysautonomia
In specific peripheral neuropathies, both autonomic and somatic nerve fibers can be damaged simultaneously:
Diabetic neuropathy: Autonomic dysfunction initially involves the parasympathetic system, then sympathetic, and eventually presents as orthostatic hypotension; somatic neuropathy with decreased reflexes develops in parallel but through separate pathophysiological mechanisms 2
Guillain-Barré Syndrome: Most patients develop generalized hyporeflexia or areflexia as a cardinal feature, and approximately 10% experience dysautonomic complications including orthostatic hypotension and blood pressure fluctuations 3
Hereditary Sensory and Autonomic Neuropathies (HSAN): Type III (familial dysautonomia) specifically presents with diminished deep tendon reflexes alongside profound autonomic dysregulation with severe orthostatic hypotension and autonomic crises 4
Drug-induced neuropathy: Bortezomib causes sensory peripheral neuropathy with suppression/reduction of deep tendon reflexes proportional to sensory loss, and separately causes dysautonomic neurotoxicity with orthostatic hypotension in approximately 10% of patients 3
Classic Dysautonomia Presentations WITHOUT Reflex Changes
Pure dysautonomic conditions do not affect deep tendon reflexes 1:
Postural Orthostatic Tachycardia Syndrome (POTS): Heart rate increase ≥30 bpm in adults (≥40 bpm in adolescents) within 10 minutes of standing without orthostatic hypotension; reflexes remain normal 3, 1
Neurogenic orthostatic hypotension: Systolic BP drop ≥20 mmHg or diastolic drop ≥10 mmHg within 3 minutes of standing; reflexes are preserved unless concurrent peripheral neuropathy exists 1, 5
Reflex syncope: Vasovagal episodes with normal neurological examination including intact reflexes 3
Diagnostic Approach When Both Are Present
When you encounter decreased reflexes with orthostatic symptoms, systematically evaluate for:
Primary peripheral neuropathy with secondary autonomic involvement: Check HbA1c, fasting glucose, vitamin B12, B6, folate, thiamine, HIV, hepatitis B/C, Lyme disease, serum protein electrophoresis, ANA, ESR, CRP, and ganglioside antibodies 1
Medication review: Tricyclic antidepressants, nitrates, antiparkinsonian medications, beta-blockers, calcium antagonists, ACE inhibitors, antipsychotics, and narcotics can precipitate dysautonomia but do not cause decreased reflexes 3, 1
Neurodegenerative disorders: Parkinson's disease, multiple system atrophy, and Lewy Body dementia can present with both autonomic failure and altered reflexes (though reflexes are often exaggerated rather than decreased) 1
Acute inflammatory demyelinating polyneuropathy: Consider Guillain-Barré when reflexes are decreased/absent with rapid progression of weakness and autonomic instability 3
Critical Clinical Pitfall
Do not assume decreased reflexes indicate dysautonomia. The presence of decreased reflexes should prompt investigation for peripheral neuropathy affecting somatic nerves, while dysautonomia requires separate evaluation through orthostatic vital signs, tilt table testing, Valsalva maneuver, and cardiac responses to deep breathing 1. A case report of multiple sclerosis with orthostatic hypotension specifically noted "exaggerated deep tendon reflexes" alongside autonomic dysfunction, demonstrating that central dysautonomia typically preserves or enhances reflexes 6.