Selective autonomic and sensory deficits in slow transit constipation

Area of Science:

• Neurology
• Gastroenterology
• Autonomic Nervous System Research

Background:

• Chronic idiopathic constipation (CIC) is a complex condition with potential autonomic dysfunction.
• Previous research suggested a link between sweating abnormalities and CIC in some patients.
• Investigating small fiber neuropathy is crucial for understanding CIC heterogeneity.

Purpose of the Study:

• To differentiate neural and sweat gland components of sweat response in CIC.
• To assess unmyelinated sensory fiber function to identify small fiber neuropathy.
• To explore the role of autonomic dysfunction in CIC pathogenesis.

Main Methods:

• Evaluated thermal thresholds and capsaicin response (axon reflex vasodilatation) using laser Doppler.
• Measured direct and axon reflex sweating (induced by methacholine and nicotine) with an evaporimeter.
• Compared 12 female CIC patients (childhood-onset vs. adult-onset) with 19 healthy controls.

Main Results:

• Four childhood-onset CIC patients showed selective unmyelinated afferent fiber deficits (elevated warm/heat pain thresholds, reduced capsaicin response).
• Seven adult-onset CIC patients exhibited selective neural sweating deficits, indicating post-ganglionic sympathetic cholinergic fiber dysfunction.
• All patients demonstrated normally functioning sweat glands in direct response to methacholine.

Conclusions:

• Severe CIC may be a manifestation of selective small fiber neuropathies.
• Distinct neuropathic patterns are associated with childhood-onset versus adult-onset CIC.
• Autonomic dysfunction, specifically small fiber neuropathy, is a key factor in a subset of CIC patients.