Median nerve

Diabetes mellitus is the most common cause of peripheral neuropathy in the United States. Approximately half of all diabetics demonstrate evidences of neuropathy. The usual clinical pattern is that of a slowly progressive, mixed sensorimotor and autonomic polyneuropathy. More acute, asymmetrical motor neuropathies are also seen, usually affecting the lumbosacral plexus, particularly in older persons with type 2 (non-insulin-dependent) diabetes mellitus. Patients with diabetes mellitus are also prone to develop isolated palsies of cranial nerve III or VII, and there is a high incidence of asymptomatic focal demyelin-ation in the distal median nerve. 

Local necrosis may occur following perivenous leakage of thiopentone. As median nerve damage has been reported following extravasation in the antecubital fossa, this site is not recommended for administration of thiopentone. If significant extravasation occurs then hyaluronidase should be infiltrated into the affected area to facilitate reabsorption. 

In addition, clay wedging, throwing, and building can cause hand and wrist injuries, including median nerve damage resulting in carpal tunnel syndrome (identified by numbness in the thumb and first three fingers). 

To minimize clay dust inhalation, it is best to buy premixed clay. Potters should change clothes before leaving their work area. Fresh clay should be used to minimize bacteria and mold growth. To avoid median nerve damage and resulting carpal tunnel syndrome, the potter s wrist should be unflexed frequently. A face mask can be worn when clay dust is present. 

Sensorimotor deficits imitating peripheral nerve involvement were reported (Back and Mrowka 2001). Ulnar and median nerve-like deficit were due to infarcts located in the thalamus and the corona radiate (Lampl et al. 1995). We have seen two patients with radial nerve-like deficits due to cortical ischemic lesions of the cortical presentation of the hand in the motor cortex. Normal nerve conduction velocity and MRI help to clarify these cases. 

Differential diagnoses of peripheral neuropathy were entertained. Laboratory tests revealed that serum parameters for electrolytes and proteins were all within the normal range. Urine porphyrinogen and porphobilinogen levels were normal. Tests were negative for serum rheumatoid factor and antinuclear antibodies, the latter used in detection of connective tissue diseases such as systemic lupus erythematosus and polyarteritis nodosa that could present with features of peripheral neuropathy. Nerve conduction studies of the radial, ulnar, and median nerves revealed delayed conduction. Biopsies of the ulnar and radial nerves showed loss of nerve fibers and sudanophilic (indicating lipid) deposits in the Schwann cells of the neurons. Similarly, the yellowish plaques of the pharynx showed abundant macrophages filled with sudanophilic material. These deposits were not membrane-bound. 

In the presence of high lithium concentrations (2.6 and 1.6 mmol/l), two patients had high amplitude of the primary complex in median nerve somatosensory evoked potentials, which normalized as concentrations fell (549). 

Vollhardt M, Ferbert A. [Influence of hypocalcemia and high serum levels of hthium on the amplitude of N20/P25 components of median nerve SEP.]EEG-Labor 1999 21 65-70. 

A 16-year-old girl had a median nerve block followed by an area of skin and fat necrosis at the site of injection and a middle-aged patient received an interscalene block resulting in subsequent fat necrosis at the injection site. 

Southworth SR, Hartwig RH. Foreign body in the median nerve a complication of acupuncture. J Hand Surg [Br] 1990 15(1) 111-12. 

Intravenous formulations are probably the least demanding of all injectates the human vein is quite robust, although venous irritancy is often encountered in clinical trials. A surprising example of this robustness is seen when inducing anesthesia with thiopental sodium (sodium thiopentone). The upper limb veins tolerate these alkaline solutions with impunity, but the solutions are very damaging when administered occasionally and iatrogenically into the cubital fossa a solution at pH 9 can cause serious injury to the structures at the elbow, including the median nerve. 

Another example of an experiment showing the sizes of the physiologically defined minicolumns is the nerve regeneration study carried out by Kaas et al. (1981). These experimenters made an initial electrode penetration of the somatic sensory hand area in a monkey s neocortex in a direction more or less parallel to the surface of the cortex and showed that over a considerable distance the same modality type is observed. They then sectioned the median nerve and allowed time for the nerve to regenerate and re-innervate of the skin. The recording experiment was then... 

Phenytoin has also been reported to cause peripheral neuropathy when used in high doses. Shorvon (S7) found that at a serum phenytoin concentration of 30 mg/liter there was a reduction in sural nerve conduction velocity in seven of nine patients and in median nerve sensory velocity in four of nine patients. It was not clear if the peripheral neuropathy was due to a toxic effect of the drug or, as seems more likely, to a folate deficiency associated wifli the anticonvulsant drug (H5). 

TTX can result in peripheral neuropathy, although this disorder is uncommon. The prevalence is generally low, depending on the duration of the condition, which is thought to be about 5% clinically, but increases to 8% in subchnical cases (Roquer and Cano, 1993). Nerve entrapment, similar to hypothyroidism, can also occur. The most common is median nerve compression, commonly known... 

RNS (at 3 Hz with square-wave pulses 0.3 ms in duration) of the facial nerve to the orbicularis oculi and orbicularis nasalis, accessory nerve to the trapezius, and median nerve to the abductor pollicis brevis muscles can be studied. Hand-held bipolar electrodes and adhesive surface electrodes are used for stimulation and recording, respectively. Routine nerve conduction studies (NCS) of all four limbs, including the VII nerve, can also be performed. 

Intravenous formulations are probably the least demanding of all injectates. Solutions of thiopental sodium are routinely administered at the induction of anesthesia, but are extremely alkaline and would be very damaging if administered subcutaneously or intramuscularly. Unfortunately, this occurs occasionally as an iatrogenic adverse event when the injection (pH 9) extravasates serious injury can easily occur to the structures in the cubital fossa (including the median nerve). 

Carpal tunnel syndrome (CTS) The result of compression of the median nerve in the carpal tunnel of the wrist. 

Sauter AR, Dodgson MS, Kalv0y H, Grimnes S, Stubhaug A, Klaastad 0. 2009. Current threshold for nerve stimulation depends on electrical impedance of the tissue A study of ultrasound-guided electrical nerve stimulation of the median nerve. Anesth Analog 108(4), 1338-1343. 

Accioli-De-Vaconcellos, Z.A., Kassar-Duchossoy, L., Mira, J.C., 1999. Long term evaluation of experimental median nerve repair by frozen and fresh nerve autografts, allografts and allografts repopulated by autologous Schwann cells. Restor. Neurol. Neurosci. 15, 17-24. 

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