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Recent technical improvements in ultrasonography including compound linear array technology, improved computer processing and dynamic imaging capabilities has allowed for the imaging of smaller joints and structures including abnormalities of nerves due to compression/entrapment and specific lesions that may be the cause of pathology. CTS is the most studied peripheral neuropathy (Buchberger, 1997) however, the pathological changes associated with injury in a number of other nerves have also been observed using ultrasound.

with a study that aimed to report the normal appearance of the median and ulnar nerves in the upper limb from cadavers and healthy participants (Fornage, 1988). A description of the normal appearance of the nerves was given from longitudinal scans, as linear

hyperechogenic structures parallel with hypoechogenic areas (Fornage, 1988) as shown in Figure 2-38.

Figure 2-38: Longitudinal sonogram of the radial nerve.

Transverse scans were also described as oval hyperechogenic structures with internal punctuated hypoechogenic areas (Fornage, 1988) as shown in Figure 2-39.

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Figure 2-39: Transverse sonogram of the median nerve

The study also differentiated the nerves from the tendons and muscles by their relative inactivity when compared to the other structures during flexion and extension movements of the arm. Grechenig, et al (2000) described the same echogenic characteristics as Fornage in the sciatic nerve in the lower limb from healthy participants and reported that the perineurium of the sciatic nerve produced a bright echo at the boundary of the nerve.

In the 1990‟s, a study that employed fifty healthy participants and 10 patients suffering

with hereditary motor and sensory neuropathy, aimed to investigated how well

ultrasonography could image peripheral nerves including the radial nerve at the humerus, the ulnar nerve distal to the cubital tunnel, the sciatic nerve in the middle of the thigh and the tibial and common peroneal nerves just distal to their bifurcation (Heinemeyer,

Reimers, 1999). The study found that in healthy subjects the ulnar and radial nerves could be identified in all cases, the sciatic nerve in 37 cases, the tibial and peroneal nerves in 10 cases. The average values given for the cross-sectional area of the arm nerves were 3 mm2 and for the sciatic nerve were 6 to 7 mm2. The study stated that ultrasonography allowed

and peroneal nerves in the lower limb. However, no significant differences were seen in nerve size and structure between patients and healthy subjects.

The ulnar nerve crosses the elbow joint within the cubital tunnel, and enters the hand

through Guyon‟s canal. Entrapment or compression of the ulnar nerve at the elbow is

known as Cubital tunnel syndrome (CuTS), a condition brought on by increased pressure on the ulnar nerve at the elbow resulting from fractures, ganglion formation and bony projections that form along the joint known as bone spurs (Ellis, et al 2002).

A study by Thoirs, et al ( 2007) aimed to test the influence of ulnar nerve measurements when discriminating between 22 limbs that were affected by ulnar nerve entrapment at the elbow and 108 healthy limbs. The study found that that the cross-sectional measurements for area and diameter of the ulnar nerve made at the level of the medial epicondyle could distinguish between healthy limbs and those affected by ulnar nerve entrapment.

Yoon, et al (2004) proposed the use of a ratio between the cross sectional area at the site of injury and at an unaffected site on the ulnar nerve to improve the diagnostic accuracy of ultrasonography in CuTS, when compared to a single measurement taken at the site of maximal enlargement of the nerve. The ratio was suggested to reduce the variables arising from individual variations such as the age, sex, weight etc of the participant in the

measurements taken by ultrasonography. The study measured the cross-sectional area of the ulnar nerve at three sites in 30 healthy participants and 26 individuals with ulnar nerve entrapment. They found that the ratio data produced values with a sensitivity of 100% (the

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proportion of people with the disorder who were correctly diagnosed) and specificity (particularly suited for the use) of 96.7% for the diagnosis of CuTS.

Nerve entrapment within Guyon‟s canal at the wrist is rare, although specific causes such

as ganglia and abnormal muscles can be demonstrated by ultrasound (Ellis, et al 2002). Nakamichi and Tachibana (1998) used ultrasonography to study the anatomy of the

Guyon‟s canal at the wrist and imaged a ganglion arising from the joint between the

triquetrum bone and the hamate bone in participants with ulnar neuropathy. The study reported that the role of ultrasonography was not only to identify the pathology but also to determine its relationship with other structures in the area.

A study that aimed to determine the capability of ultrasonography to image radial neuropathy caused by a fracture in the humerus was performed by Bodner, et al (2001) using 11 patients with radial nerve deficiency after a humeral fracture and 10 healthy participants. The study found that ultrasonography could detect an abrupt change in course of the nerve around the fractured area which was confirmed in 5 patients during surgery.

In the lower limb, the sciatic nerve and its major branches can become compressed or entrapped by a variety of soft tissue masses. Displacement of the nerve from its normal course is the main ultrasound sign but ischial bursitis (inflammation of the hip joint) can also irritate the sciatic nerve, producing compressive-like symptoms (Ellis, et al 2002). The peroneal nerve, as it winds around the fibular neck and the tibial nerve, within the tarsal tunnel at the ankle joint, can become compressed or entrapped. This is the result of pathologies that include ganglia, soft tissue tumors, tenosynovitis and fracture deformity.

anatomy of the sciatic nerve and its division into the tibial and peroneal nerves. The study involved 74 participants who were scanned at the popliteal fossa at the back of the thigh and the distance of the joint to the tibial and peroneal nerve division was measured using a caliper. The sciatic nerve and its division were visualized in 53 of 74 (72%) participants and a significant correlation was shown between the width of the knee-joint line and the depth of the nerve division.