Anhidrosis

Specialty: Neurology.

• absence of sweating
• focal or generalized hypohidrosis

Why it occurs

• Peripheral autonomic neuropathy (diabetic, amyloid or immune-mediated)
• Unilateral Horner syndrome (lesion of the cervical sympathetic pathway that produces miosis, ptosis and facial anhidrosis)
• Ross syndrome (rare autonomic disorder characterized by segmental anhidrosis, tonic pupils, and areflexia)
• Multiple system atrophy (preganglionic involvement of the intermediate spinal cord)
• Traumatic spinal cord injury above mid-thoracic levels (produces anhidrosis below the level of injury)

Initial workup

Quantitative Sudomotor Axonal Reflex Test (QSART); sweat test with thermochromic indicator powder (alizarin) exposed to ambient heat; skin biopsy to quantify sweat gland innervation; MRI of the spine and neck if spinal cord injury or structural Horner syndrome is suspected.

Standard management

• There are no drugs that restore sudomotor function if there is denervation of the sweat glands
• Rigorous preventive physical measures — avoid sun exposure and high temperatures, use of damp clothing, constant hydration with cold liquids, active air conditioning
• Treatment of underlying neuropathy.