9606080651/653/654 ELECTROPHYSIOLOGICAL FINDINGS OF SYMPTOMATIC AND ASYMPTOMATIC CARPAL TUNNEL SYNDROME IN PATIENTS WITH DIABETES MELLITUS
ABSTRACT:
CTS develops due to the abnormal compression of the median nerve in the carpal tunnel of the hand and is frequently observed in individuals engaged in excessive manual activities. CTS pathology features tendon injury, swelling, pain, and inflammation in the palm and wrist areas . In DM patients, the risk of developing CTS increases proportionally with the length of DM pathology, indicating gradual degeneration of the carpal tunnel surrounding bones and ligaments during the course of the disease. Furthermore, DM patients with DPN exhibit an accelerated risk of developing CTS compared to their non-DPN counterparts. Generally, CTS is more common in chronic T2DM patients with co-existing DPN pathology According to a statistical report, the rate of prevalence of CTS is only 2% among the general population, while that rises to 14% in T2DM patients without DPN and 30% in case of T2DM combined with DPN.
INTRODUCTION:
Diabetes mellitus (DM) is a metabolic disease, involving inappropriately elevated blood glucose levels. DM has several categories, including type 1, type 2, maturity-onset diabetes of the young (MODY), gestational diabetes, neonatal diabetes, and secondary causes due to endocrinopathies, steroid use, etc. The main subtypes of DM are Type 1 diabetes mellitus (T1DM) and Type 2 diabetes mellitus (T2DM), which classically result from defective insulin secretion (T1DM) and/or action (T2DM). T1DM presents in children or adolescents, while T2DM is thought to affect middle-aged and older adults who have prolonged hyperglycemia due to poor lifestyle and dietary choices. The pathogenesis for T1DM and T2DM is drastically different, and therefore each type has various etiologies, presentations, and treatments.
Median nerve entrapment at the wrist is the most common of all entrapment neuropathies and, consequently, is one of the most frequent reasons for referral for an electrodiagnostic (EDX) study. In nearly all patients, the usual site of compression occurs in the carpal tunnel and results in a constellation of symptoms and signs known as the carpal tunnel syndrome (CTS). Lesions of the C6–C7 nerve roots or, less often, the brachial plexus and the proximal median nerve may be confused clinically with median neuropathy at the wrist, especially in early or mild cases.
CARPAL TUNNEL SYNDROME: Patients with CTS may present with a variety of symptoms and signs. Women are affected more often than men. Although CTS usually is bilateral both clinically and electrically, the dominant hand usually is more severely affected, especially in idiopathic cases. Patients complain of wrist and arm pain associated with paresthesias in the hand. The pain may be localized to the wrist or may radiate to the forearm, arm, or, rarely, the shoulder; the neck is not affected. Some patients may describe a diffuse, poorly localized ache involving the entire arm. Paresthesias are frequently present in the median nerve distribution (medial thumb, index, middle, and lateral ring fingers). Although many patients report that the entire hand falls asleep, if asked directly about little finger involvement, most will subsequently note that the little finger is spared.
ETIOLOGY: The reported causes of CTS are numerous. Despite this exhaustive list, most cases are idiopathic. Indeed, idiopathic cases present with the same signs and symptoms as CTS caused by the other conditions. Although the etiology of idiopathic cases was long considered to be tenosynovitis of the transverse carpal ligament, pathologic evaluation typically shows little evidence of inflammation. In most cases, edema, vascular sclerosis, and fibrosis are seen, findings consistent with repeated stress to connective tissue. Compression results in symptoms by way of ischemia and demyelination and, if it is severe enough, wallerian degeneration and axonal loss. Occupations or activities that involve repetitive hand use clearly increase the risk of CTS (e.g., typists, data entry workers, mechanics, and carpenters). The conditions most often associated with CTS, other than idiopathic, are diabetes, hypothyroidism, rheumatoid arthritis, amyloidosis, and pregnancy. One important clue to an underlying cause, other than idiopathic, is the presence of CTS in the non-dominant hand. In idiopathic cases, the dominant hand is nearly always the affected hand; if symptoms are bilateral, then the dominant hand is more affected than the contralateral hand. CTS that is significantly worse in the non-dominant hand should raise a red flag to a specific underlying cause other than idiopathic CTS.
DIFFERENTIAL DIAGNOSIS: There are several peripheral as well as central nervous system (CNS) lesions that may result in symptoms similar to CTS. The peripheral lesions that enter into the differential diagnosis include median neuropathy in the region of the elbow, brachial plexopathy, and cervical radiculopathy. The most common among the disorders that may be confused with CTS is cervical radiculopathy, especially lesions of the C6 or C7 root, which may cause both pain in the arm and paresthesias similar to those that characterize CTS. The important clinical clues that suggest radiculopathy rather than CTS are pain in the neck, radiation from the neck to the shoulder and arm, and exacerbation of symptoms by neck motion. Key points in the physical examination that suggest radiculopathy are abnormalities of the C6–C7 reflexes (biceps, brachioradialis, triceps), diminished power in proximal muscles (especially elbow flexion, elbow extension, arm pronation), and sensory abnormalities in the palm or forearm, which are beyond the distribution of sensory loss found in CTS.
ELECTROPHYSIOLOGIC EVALUATION: The electrophysiologic evaluation of a patient suspected of having CTS is directed toward the following: 1. Demonstrating focal slowing or conduction block of median nerve fibers across the carpal tunnel 2. Excluding median neuropathy in the region of the elbow 3. Excluding brachial plexopathy predominantly affecting the median nerve fibers 4. Excluding cervical radiculopathy, especially C6 and C7 5. If a coexistent polyneuropathy is present, ensuring that any median slowing at the wrist is out of proportion to slowing expected from the polyneuropathy alone.
Nerve Conduction Studies: The pathophysiology of CTS typically is demyelination, which, depending on the severity, may be associated with secondary axonal loss. In moderate to advanced cases, the electrodiagnosis usually is straightforward. On routine median studies, a demyelinating lesion at the carpal tunnel results in slowing of the distal motor and sensory latencies. If there is either demyelination with conduction block or axonal loss, the distal compound muscle action potential (CMAP) and sensory nerve action potential (SNAP) amplitudes, stimulating the median nerve at the wrist, will be decreased as well. In patients with typical CTS, the median distal motor and sensory latencies, and minimum F wave latencies, are moderately to markedly prolonged. However, there are a group of patients with clinical symptoms and signs of CTS in whom these routine studies are normal (approximately 10–25% of CTS patients). In such patients, the electrodiagnosis of CTS will be missed unless further testing is performed using more sensitive nerve conduction studies. Those studies usually involve a comparison of the median nerve to another nerve in the same hand. The ulnar nerve is the nerve most commonly used for comparison; less often the radial nerve is used. The common median-versus-ulnar comparison tests are (1) median-versus-ulnar palm-to-wrist mixed nerve latencies, (2) median-versus-ulnar wrist-to-digit 4 sensory latencies, and (3) median (second lumbrical)-versus-ulnar (interossei [INT]) distal motor latencies. In each of the comparison studies, identical distances between the stimulator and recording electrodes are used for the median and ulnar nerves. These techniques create an ideal internal control in which several variables that are known to affect conduction time are held constant, including distance, temperature, age, and nerve size. Ideally, the only factor that varies in these paired median-versus-ulnar comparison studies is that the median nerve traverses the carpal tunnel, whereas the ulnar nerve does not. Thus, any preferential slowing of the median nerve compared with the ulnar nerve can be attributed to conduction slowing through the carpal tunnel.
CONCLUSION:
In conclusion, this study establishes Diabetes mellitus as a major risk factor in the development of Carpal Tunnel Syndrome as the incidence of CTS is significantly high among the diabetic patients. We strongly recommend-early screening of diabetes patients with nerve conduction study to detect carpal tunnel syndrome.