Yasusuke Hirasawa

Causalgia and Reflex Sympathetic Dystrophy

In 1867 Mitchell [141] coined the term “causalgia” to describe burning pains experienced following nerve injury caused by a gunshot wound. In 1900 Sudeck [197] reported acute bone atrophy occurring after trauma, and in 1946 Steinbrocker [193] used the term “shoulder hand syndrome” to describe pains and swellings in the upper extremities that occur after myocardial infarction. Evans first used the term reflex sympathetic dystrophy (RSD) in his report published in 1947 [45].

Diagnosis of Peripheral Nerve Injury and Entrapment Neuropathy

With the exception of an open injury, in which the nerve trunk is lacerated, surgical treatment of peripheral nerve paralysis is performed conservatively from 1 to 3 months after injury. This is to allow enough time for the patient to recover from the so-called contusion state, the hemorrhage around the injured nerve to be absorbed, the edema to disappear, inflammatory signs to subside, and the state of the nerve paralysis to be clarified. In other words, surgery should be considered once the recovery process slows down and stops. From various data, such as sensory tests, manual muscle tests, sweating test, progression of Tinel’s sign, and electro-physiological findings, effective criteria can then be determined for evaluating the patient. It is important that these neurological tests be performed once every 3 weeks to periodically determine the state of injury of the nerves and the degree of recovery.

Ulnar Nerve Injury and Entrapment

The ulnar nerve originates from the medial cord of the brachial plexus (C8, Th1), runs down along the ulnar side of the arm, and comes out to the flexor-ulnar side of forearm after passing through the sulcus nervi ulnaris at the medial epicondyle of the humerus. It further runs down to the ulnar side of forearm and reaches the palm thorough the Guyon canal (Fig. 1).

Radial Nerve Injury and Entrapment

The radial nerve, which innervates the upper limb together with the median nerve and the ulnar nerve, is one of the most important peripheral nerves. Its damage can cause loss of active extension error of the wrist and digits. Because it runs along the humerus, it is susceptible to damage by compression and fractures. Entrapment neuropathy may occur, because it passes through the anatomical entrapment point around the elbow joint.

Nerve Injury in the Hand

The peripheral nerves of the hand include the median nerve, the ulnar nerve, and the sensory branch of the radial nerve. The median nerve and the ulnar nerve produce their motor branches to the intrinsic muscles of the hand at the level of the carpal bones. Their sensory branches become the proper palmar digital nerves and they are distributed to the fingers. The median nerve innervates the palmar side of the thumb, the index finger, the middle finger, and the radial side of the ring finger. The ulnar nerve innervates the little finger and the ulnar side of the ring finger. However, there are some anomalous innervations regarding the sensory area. For example, the ulnar nerve sometimes innervates the radial side of the ring finger and the middle finger. The palmar digital nerves innervate the dorsal skin of the digits (except the thumb), which is distal from the mid-metacarpus. The proper palmar digital nerve to the thumb is distributed only to the palmar side and the nail bed. The dorsal aspect of the thumb is innervated by the sensory branch of the radial nerve.

Nerve Injury and Entrapment Neuropathy Around the Shoulder

The movement of the shoulder girdle is controlled by three anatomical joints (scapulohumeral joint, acromio-clavicular joint, and sternoclavicular joint) and two functional joints (subacromial joint and scapulothoracic joint). By cooperation of the muscles that move these joints, the shoulder girdle can be moved smoothly.

Nerve Injury and Entrapment in the Lower Extremity

The lower limb is innervated by the lumbar plexus and the sacral plexus. The lumbar plexus consists of L2, L3, and L4, which divide to form the lateral cutaneous nerve of the thigh, the femoral nerve, and the obturator nerve. The sacral plexus consists of L4, L5, S1, S2, and S3 and forms the sciatic nerve (Fig. 1).

Basic Research on Peripheral Nerve Injury and Regeneration

The Italian histologist Golgi [57] developed a method to stain nerve cells in 1894. Cajal [23] in Spain performed histological analysis of the central nervous system using Golgi stain and established the basis of neurological investigations.

Treatment of Peripheral Nerve Injury and Entrapment Neuropathy

Peripheral nerve paralysis is caused by various factors, such as compression, contusion, entrapment, laceration, drug injection, and traction. The prognosis varies greatly, depending on the location of the injury, the mechanism of injury, and accompanying injury.

Tumors of Peripheral Nerves

Of the cells that constitute peripheral nerves, those that develop tumors are mostly Schwann cells. Infrequently, however, some tumors originate from peripheral nerve cells. Because Schwann cells differentiate in different ways, histological profiles of the tumors are also diverse. Benign tumors are often schwannomas, neurilemomas, or neurofibromas. The incidence of solitary schwannoma is relatively high, and it is often encountered clinically when lesions arising in the spinal cord are included. Neurofibroma is known to occur in association with von Recklinghausen’s disease, but its solitary occurrence is also not rare. Among malignant tumors, malignant schwannoma is well known, but malignant tumors that arise in the nerve sheath and are composed mainly of spindle cells have recently come to be collectively called malignant peripheral nerve sheath tumors (MPNST). The proportion of MPNST in all malignant tumors of soft tissue is not large. Slightly less than two-thirds of them are neurofibromas associated with von Recklinghausen’s disease, especially plexiform neurofibroma, that has become malignant. Benign and malignant Triton tumors, which show striated muscle formation, are considered to develop as a result of special differentiation of Schwann cells. Schwann cells may become epithelioid or melanin-producing, or they may form tumors resembling melanoma.