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Classification and staging of diabetic neuropathy

Class I Subclinical Neuropathy*

Abnormal electrodiagnostic tests (EDX)
Decreased nerve conduction velocity
Decreased amplitude of evoked muscle or nerve action potential

Abnormal quantitative sensory testing (QST)
Thermal warming/cooling

Abnormal autonomic function tests (AFT)
Diminished sinus arrhythmia (beat-to-beat heart rate variation)
Diminished sudomotor function
Increased pupillary latency

Class II Clinical Neuropathy
Diffuse neuropathy
Distal symmetric sensorimotor polyneuropathy
Primarily small fiber neuropathy
Primarily large fiber neuropathy

Autonomic neuropathy
Abnormal pupillary function
Sudomotor dysfunction
Genitourinary autonomic neuropathy
Bladder dysfunction
Sexual dysfunction
Gastrointestinal autonomic neuropathy
Gastric atony
Gall bladder atony
Diabetic diarrhea
Hypoglycemic unawareness (adrenal medullary neuropathy)
Cardiovascular autonomic neuropathy
Hypoglycemic unawareness

Focal neuropathy
Mononeuropathy (upper or lower extremity)
Mononeuropathy multiplex
Polyradiculopathy (can occur with diffuse neuropathy)
Cranial mononeuropathy

* Neurological function tests are abnormal, but no neurological symptoms or clinically detectable neurological deficits indicative of a diffuse or focal neuropathy are present. Class I "Subclinical neuropathy" is further subdivided into Class Ia if an AFT or QST abnormality is present, Class Ib if EDX or AFT and QST abnormalities are present, and Class Ic if an EDX and either AFT or QST abnormalities or both are present.
Adapted from Consensus Panel: Report and Recommendations of the San Antonio Conference on Diabetic Neuropathy. Diabetes 1988; 37:1000.