by Nicole Evans M.D.

Created on: October 18, 2009   Last Updated: April 04, 2010

Carpal tunnel syndrome results from dysfunction of the median nerve that runs through your wrist. The median nerve innervates specific muscles and sensory abilities in sections of your hands and fingers.

Diagnostic criteria for carpal tunnel syndrome:

The formal diagnosis of carpal tunnel syndrome requires the presence of one or more of the below symptoms plus one or more of the objective findings listed below.

Symptoms used to diagnose carpal tunnel syndrome:

-Parasthesias (pins and needle sensation) in the median nerve distribution

-Hyposthesias (decrease sensation to light touch) in the median nerve distribution

-Pain in the median nerve distribution

-Numbness in the median nerve distribution

Objective findings used to diagnose carpal tunnel syndrome:

-Positive Tinel's test (tapping the median nerve at the wrist reproduces the symptoms)

-Positive Phalen's test (pressing the backs of the hands together with wrists flexed reproduces the symptoms in 30 to 60 seconds)

-Decreased or absent sensation to sharp pinprick in the median nerve distribution

-Nerve conduction study indicating dysfunction of the median nerve across the carpal tunnel in the wrist.

Other diagnoses if the above diagnostic criteria for carpal tunnel syndrome are not met:

There are several other conditions that can cause similar symptoms or even identical symptoms. However, these conditions will often have other symptoms in addition to those listed above and a negative Tinel's or Phalen's test.

The differential diagnoses include, but are not limited to:

-Cervical radiculopathy (dysfunction of the nerves occurring at the nerve roots where they exit the cervical vertebrae)

-Brachial plexitis (dysfunction at the brachial plexus, a network of nerves between the neck and the shoulder)

-Vitamin B6 deficiency (rare, consider in those taking Isoniazid)

-Vitamin B6 toxicity (seen at supplementation over 1000 grams a day)

-Riboflavin deficiency (a B vitamin required to turn B6 into its active form, consider in those with malabsorption syndromes and dairy free diets)

-Early disseminated Lyme disease (many other associated symptoms)

-Glue sniffing (consider this dangerous diagnosis particularly in kids and teens)

-Adverse effect from medications (many medicines can cause parasthesias, common ones are metronidazole [Flagyl] and gabapentin [Neurontin])

Certain risk factors may assist your physician in making an accurate diagnosis of carpal tunnel syndrome. A history of chronic repetitive wrist or finger motion or compression at the wrist is an obvious factor to consider. But additional risk factors include:

-Obesity

-Diabetes mellitus

-Hypothyroidism

-Connective Tissue Diseases

-Hereditary Neuropathies

-Third trimester of pregnancy

Keep in mind that an individual may have carpal tunnel syndrome in addition to one or more of the above conditions. Nerve conduction studies can assist in locating exactly where the nerve dysfunction lies. 

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