Needle electromyography is used to detect axon loss which is chronic unless there is a super added acute external pressure on an existing entrapped nerve. Routine tests include sensory motor conductions across the wrist in median and ulnar nerves.
Peripheral Nerve Entrapment and their Surgical Treatment
When the terminal motor latency of the median nerve to the Abductor Pollicis Brevis muscle is prolonged it is termed as moderate CTS. When routine tests are negative for CTS but symptoms are very suggestive, sensitive internal comparative tests are done which compare the SNAP from the median nerve to that recorded from the Radial and Ulnar nerves to demonstrate differential slowing across the wrist only in the median nerve.
This term is reserved for compression of the Ulnar nerve in the cubital tunnel distal to the medial epicondyle in the forearm. Nerve conduction study would show variable loss in the amplitude of the Ulnar SNAP, depending on the severity of the entrapment. Motor conduction would localise the site of the nerve entrapment and quantify the axon loss if any.
Needle Electromyography would detect the chronicity of the lesion and localise it specially if there is chronic long-standing entrapment with severe axon loss. Electrodiagnosis would localise the site of the lesion to the lower trunk of the brachial plexus. Chronic entrapment of the posterior interosseous nerve shows normal radial sensory conduction with chronic denervation in the muscles supplied by that nerve. It is the most common entrapment neuropathy in our clinical practice in India.
Although national data is missing over here, there is data from USA to show that there too it is the most common compressive neuropathy. The carpal tunnel situated in the proximal palm, it contains the median nerve and nine flexor tendons from the forearm into the palm. The tendons are covered by a variable amount of tenosynovium, the role of this in the pathology is alluded to the above. The tunnel is bounded by the carpal bones dorsally and the transverse carpal ligament, a fibrous unyielding structure, volarly.
The median nerve lies superficially in the carpal tunnel, immediately beneath the transverse carpal ligament. The palmar cutaneous nerve branches 5 cm proximal to the wrist crease and passes into the palm above the ligament. The median nerve divides into sensory and motor branches after passing through the carpal tunnel, the motor branch lying volarly and radially in the nerve. There are multiple causes discussed without consensus about them.
Where no specific cause exists it is primary CTS. These are generally women in the age group of 30—50 years. Graham et al [ 22 ] have published the six most important symptoms to diagnose CTS:. Initial treatment can be symptomatic, comprising of rest, avoidance of vibratory tools, or repetitive activity. Changing work profile and drug therapy which can be a combination of NSAIDs and oral as well as local steroids. A substantial majority though require surgical release. Nonsurgical treatment is an option for early CTS. Surgery is an option when there is evidence of median nerve denervation.
A second nonsurgical treatment or surgery is recommended when initial nonsurgical treatment fails after weeks. There is no evidence to support specific treatment recommendations for CTS associated with diabetes, cervical radiculopathy, hypothyroidism, polyneuropathy, pregnancy, rheumatoid arthritis or CTS in the workplace. Surgical treatment with complete division of the flexor retinaculum is recommended, regardless of the technique used.
Skin nerve preservation, epineurotomy, flexor retinacular lengthening, internal neurolysis, tenosynovectomy, and ulnar bursa preservation are not recommended in the performance of carpal tunnel surgery. Wrist immobilization is not recommended postoperatively after routine carpal tunnel release. No recommendation is made regarding use of postoperative rehabilitation.
It is suggested that physicians use one or more patient response tools to assess results after carpal tunnel treatment in performing research. Once the decision is made based on clinical findings and electrophysiology the treatment consists of Carpal Tunnel Release. There are three main techniques to perform this procedure. There is no difference in outcome from either[ 21 ] as far as decompression of the nerve is concerned or therefore the relief from symptoms but there is considerable difference in the postoperative morbidity and recovery process.
The 2 nd and 3 rd method have considerably lower morbidity as compared to the older conventional wide exposure which crosses the wrist crease.
Between the minimal access and endoscopic release there is not much to choose in terms of the small incision; however, the endoscopic technique has reported higher complication rate vis-a-vis accidental nerve damage. The minimal access open technique is therefore the author's preferred choice.
Nerve entrapment - Physiopedia
The incision is taken in the radial aspect of the 4 th ray starting from 1 cm distal to the wrist crease for a further 2 cm. It is important not to cross the wrist crease to avoid scar morbidity due to continuous wrist movement. The layers are. The retractor is then repositioned so that the volar carpal ligament and the distal deep fascia of the forearm in continuity with it is visible with a properly positioned light. The incision of the volar carpal ligament in the palm is started with a no.
After this a blunt tipped but sharp straight scissor is advanced with one blade under the roof of the tunnel and the other above it. Under vision the complete volar carpal ligament and the deep fascia of the distal forearm in continuity with it is divided with one quick movement [ Figure 7 ].
The scissor is withdrawn and the division inspected to rule out and remaining strand, if found this is cut sharply. The distal part of the palmar aponeurosis is then cut under vision till the superficial palmar arch is seen [ Figure 8 ]. This is the end of the release. In the end the median nerve and its motor branch is inspected for continuity and the other contents noted. Unless the synovium is abnormally thick such patients complain of an inability to make a fist preoperatively it is left alone. If the patient has mentioned an inability to make a fist then a limited synovectomy is done until tendons are clearly seen.
For the proximal synovium a separate transverse incision may be needed on the wrist [ Figure 9 ], if there is considerable hypertrophy.
Sometimes incidental findings like seeing a large lumbrical belly [ Figure 10 ] originating in the FDP within the carpal tunnel is noted but is left alone. This is removed at 48 h and replaced with a strap on splint, which is removable. This is, used by the patient as per his or her comfort levels. Typically patients give up the splint in 2 weeks. An excellent review article on this subject by Dang et al [ 23 ] has listed the various areas.
Possible areas for median nerve compression proximal to the carpal tunnel:. Anomalous arteries, and anomalous muscles such as Gantzer's muscle, an accessory FPL muscle. The last two remain the two most frequently referenced compression neuropathies of the median nerve in the forearm.
Pronator syndrome PS commonly refers to compression of the median nerve as it passes between the two heads of the pronator teres muscle or under the proximal edge of the proximal FDS arch. Symptoms usually have an insidious onset and typically are not diagnosed as part of an overall clinical syndrome for months to years. Pain on resisted pronation from a neutral position, especially as the elbow is extended. If resisted contraction of the FDS to the middle finger reproduces symptoms, median nerve compression at the level of the fibrous arch between the heads of the FDS might be suspected.
If symptoms are elicited by resisted flexion of the forearm in full supination, compression at the more proximal level of the lacertus fibrosus might be considered.
- Treatment of Nerve Injury and Entrapment Neuropathy | Y. Hirasawa | Springer.
- MR Neurography of Neuromas Related to Nerve Injury and Entrapment with Surgical Correlation;
- Nerve Compression Injuries.
- General Diagnostic Approach;
Electrodiagnostic studies can be useful in the diagnosis of PS in that they may exclude other sites of nerve compression or help identify a double-crush with a more proximal lesion in the neck. Surgery is usually not necessary to treat PS. Conservative therapy should be tried first. This includes. Surgery is indicated after adequately long trial several months is given to conservative therapy.