Manual of Surgery Volume First: General Surgery. Sixth Edition.

by Alexis Thomson; Alexander Miles

Tetanus

Tetanus is a disease resulting from infection of a wound by a specific micro-organism, the bacillus tetani, and characterised by increased reflex excitability, hypertonus, and spasm of one or more groups of voluntary muscles.

Etiology and Morbid Anatomy.—The tetanus bacillus, which is a perfect anaërobe, is widely distributed in nature and can be isolated from garden earth, dung-heaps, and stable refuse. It is a slender rod-shaped bacillus, with a single large spore at one end giving it the shape of a drum-stick ([Fig. 26]). The spores, which are the active agents in producing tetanus, are highly resistant to chemical agents, retain their vitality in a dry condition, and even survive boiling for five minutes.

The organism does not readily establish itself in the human body, and seems to flourish best when it finds a nidus in necrotic tissue and is accompanied by aërobic organisms, which, by using up the oxygen in the tissues, provide for it a suitable environment. The presence of a foreign body in the wound seems to favour its action. The infection is for all practical purposes a local one, the symptoms of the disease being due to the toxins produced in the wound of infection acting upon the central nervous system.

The toxin acts principally on the nerve centres in the spinal medulla, to which it travels from the focus of infection by way of the nerve fibres supplying the voluntary muscles. Its first effect on the motor ganglia of the cord is to render them hypersensitive, so that they are excited by mild stimuli, which under ordinary conditions would produce no reaction. As the toxin accumulates the reflex arc is affected, with the result that when a stimulus reaches the ganglia a motor discharge takes place, which spreads by ascending and descending collaterals to the reflex apparatus of the whole cord. As the toxin spreads it causes both motor hyper-tonus and hyper-excitability, which accounts for the tonic contraction and the clonic spasms characteristic of tetanus.

Fig. 26.—Bacillus of Tetanus from scraping of a wound of finger, × 1000 diam. Basic fuchsin stain.

Clinical Varieties of Tetanus.—Acute or Fulminating Tetanus.—This variety is characterised by the shortness of the incubation period, the rapidity of its progress, the severity of its symptoms, and its all but universally fatal issue in spite of treatment, death taking place in from one to four days. The characteristic symptoms may appear within three or four days of the infliction of the wound, but the incubation period may extend to three weeks, and the wound may be quite healed before the disease declares itself—delayed tetanus. Usually, however, the wound is inflamed and suppurating, with ragged and sloughy edges. A slight feverish attack may mark the onset of the tetanic condition, or the patient may feel perfectly well until the spasms begin. If careful observations be made, it may be found that the muscles in the immediate neighbourhood of the wound are the first to become contracted; but in the majority of instances the patient's first complaint is of pain and stiffness in the muscles of mastication, notably the masseter, so that he has difficulty in opening the mouth—hence the popular name “lock-jaw.” The muscles of expression soon share in the rigidity, and the face assumes a taut, mask-like aspect. The angles of the mouth may be retracted, producing a grinning expression known as the risus sardonicus.

The next muscles to become stiff and painful are those of the neck, especially the sterno-mastoid and trapezius. The patient is inclined to attribute the pain and stiffness to exposure to cold or rheumatism. At an early stage the diaphragm and the muscles of the anterior abdominal wall become contracted; later the muscles of the back and thorax are involved; and lastly those of the limbs. Although this is the typical order of involvement of the different groups of muscles, it is not always adhered to.