Unless completely removed at an early stage, recurrence inevitably takes place.
Primary carcinoma may also occur in a supernumerary thyreoid, and in the para-thyreoid glands.
We have met with a case of _paraffin epithelioma_ on the neck, and a similar type of epithelioma may be met with in a lupus or a burn of long standing.
#The Thymus Gland.#--The thymus gland begins to diminish in size towards the end of the second year, and by the time p.u.b.erty is reached it has entirely disappeared. In some cases, however, the process of involution fails to take place, and the gland may even undergo hyperplasia and exert pressure on the trachea, the great blood vessels, or the left vagus nerve and its recurrent branch. The enlargement of the thymus may be part of a general lymphatic hyperplasia--known as the _status lymphaticus_.
The pressure effects may be entirely referable to the trachea--_thymus stenosis of the trachea_--giving rise to progressive dyspna accompanied by stridor, with paroxysmal exacerbations during which the child becomes asphyxiated. It is only expiration that is interfered with, as with each inspiratory effort the gland is sucked in towards the mediastinum and so frees the air-pa.s.sages, while with expiration it rises again, and, becoming jammed in the upper opening of the thorax, exerts pressure on the trachea, and during expiration a soft swelling is sometimes recognisable in the episternal notch. The paroxysms occur at irregular intervals, and any one of them may prove fatal. In some cases the symptoms seem to be a.s.sociated with pressure on the blood vessels and nerves rather than on the air-pa.s.sages, and in these there is distension of the veins and a tendency to syncopal attacks.
The only way to afford relief is to expose the gland and withdraw it from behind the sternum by making traction on its capsule. If the breathing is not thereby improved, the capsule should be opened and the gland sh.e.l.led out.
The term _thymic asthma_ has been applied to another form of disturbed respiration due to a large thymus, which comes on suddenly in infants otherwise apparently healthy. Without warning, the child seems to choke, has great difficulty in breathing, with inspiratory stridor and indrawing of the epigastrium; he rapidly becomes cyanosed, and in the majority of cases dies in a few minutes--_thymus death_. No satisfactory explanation of the sudden onset of the symptoms is forthcoming, but it appears to be a.s.sociated with something which suddenly narrows the mediastinal s.p.a.ce, such as backward bending of the head, or venous engorgement of the thymus gland. Cases are recorded in which an attack has come on during the administration of a general anaesthetic; in some instances the patient has suffered from the generalised status lymphaticus.
#Tumours of the Carotid Gland or Glomus Carotica# (_Potato-like tumour of the neck_).--The carotid gland under normal conditions is about the size of a grain of corn, and lies to the posterior aspect of the bifurcation of the carotid. It is sometimes the seat of _endothelioma_. The tumour has a definite capsule, is moderately firm and elastic, increases in size slowly and gradually for a time, and then may grow more rapidly. Its relation to the vessels is characteristic: as it grows it envelops the common carotid and its branches, and becomes adherent to the internal jugular vein; and it may come to implicate the nerves in the neck, particularly the vagus and its recurrent branch, and the cervical sympathetic.
It gives rise to few symptoms, and in the majority of cases the surgeon is consulted on account of the disfigurement resulting from the presence of the swelling in the neck. This swelling is ovoid, smooth or slightly lobulated; it lies at the level of the bifurcation of the carotid, and tends to grow upwards rather than downwards; it is movable from side to side, but not up and down; it lies under the sterno-mastoid, and the skin is not implicated. There is transmitted pulsation in the tumour, but no expansion.
The diagnosis has to be made from lymphoma, adenoma, tuberculous glands, sarcoma, and carcinoma.
In a large proportion of the cases operated upon it has been necessary to ligate the carotids and to excise portions of the internal jugular vein, and as severe cerebral symptoms are liable to ensue the mortality has. .h.i.therto been high. Operation is therefore only to be recommended when the growth is rapid, or the symptoms have become urgent.
CHAPTER XXVII
THE THYREOID GLAND
Surgical Anatomy--Physiological hyperaemia--Acute thyreoiditis--GOITRE--Varieties: _Parenchymatous_; _Adenomatous_; _Cystic_; _Malignant_; _Toxic_.
#Surgical Anatomy.#--The _thyreoid gland_ consists of two lateral lobes connected by an isthmus. The lateral lobes lie in contact with the side of the larynx up to the middle of the thyreoid cartilage, and with the sides of the first five or six rings of the trachea. The isthmus lies in front of the second, third and fourth rings of the trachea, and from it a process of gland tissue--the _pyramidal lobe_--pa.s.ses up in the middle line towards the hyoid bone.
The gland lies under cover of the superficial muscles of the neck, and is surrounded by a process of the cervical fascia--the external thyreoid capsule of Kocher--which connects it with the larynx, trachea, and sophagus, so that it moves with these structures on swallowing. In this capsule are numerous veins; and in the groove between the sophagus and trachea the recurrent (laryngeal) nerve runs. Enclosing the gland substance is the capsule proper, which sends in processes to form its fibrous stroma. The arteries of supply--the superior and inferior thyreoids--are very large for the size of the gland, and enter it at its four corners. The thyreoidea ima, when present, goes to the isthmus. Isolated nodules of thyreoid tissue--_accessory thyreoids_--are sometimes met with in different parts of the neck; they are liable to the same diseases as the main gland.
The secretion of the gland is absorbed into the general circulation through the veins; it consists of a complex colloid substance which contains an iodine-alb.u.min--iodothyrin--and plays an important part in maintaining the normal metabolism of the body, particularly of the central nervous and cutaneous tissues in adults, and of the bones in children. Disturbance of the function of the thyreoid gland plays a part in producing the symptoms characteristic of myxdema, cretinism, and goitre.
The _para-thyreoid glands_--usually two on each side--lie in the external capsule along the posterior edge of the lobes of the thyreoid. They are flattened, elliptical bodies, averaging a quarter of an inch in length and an eighth of an inch in width, of a light brown colour, smooth and glistening on the surface, and of a soft, flabby consistence (W. G. MacCallum). When tetany follows operations for goitre it is due to the removal of these glands.
#Physiological Hyperaemia.#--The thyreoid varies greatly in size even within normal limits, and may become engorged and swollen from physiological causes, particularly in the female. Before the onset of menstruation at p.u.b.erty, for example, the thyreoid frequently becomes engorged, and the enlargement may recur with each period for months or even years. During pregnancy also the gland may become swollen.
#Acute Thyreoiditis# may occur in a healthy thyreoid or in one that is the seat of goitre, and may end within a few days in resolution, or go on to suppuration. It is due to infection with pyogenic bacteria, which usually gain access to the gland by the blood stream, as, for example, in typhoid fever, pyaemia, influenza, and other acute infective diseases. Direct infection sometimes occurs from an abscess, a cellulitis, or an infected wound in the neck; it has also occurred from a foreign body impacted in the sophagus ulcerating through and perforating the gland.
One lobe is usually more involved than the other, but the condition may be diffused. When pus forms it may infiltrate the stroma of the gland, or may be collected into several small foci.
_Clinical Features._--The usual signs of inflammation are present; there is severe headache of a congestive nature, and sometimes vertigo. The swelling takes the shape of the thyreoid, and although the skin may not be red, the subcutaneous veins are dilated. In severe cases there is pain and difficulty in swallowing and dyspna.
When suppuration ensues, all the symptoms are aggravated, and repeated rigors occur. The pus may burst into the cellular tissue of the neck, or into the air-pa.s.sage or the sophagus.
_Treatment._--In the non-suppurative stage the ordinary treatment of acute inflammatory conditions is employed; if pus forms, the abscess should be opened and drained.
#Tuberculous and syphilitic affections# of the thyreoid are very rare.
PARENCHYMATOUS GOITRE OR BRONCHOCELE
The term goitre is applied clinically to any non-inflammatory enlargement of the thyreoid gland.
_Etiology._--Parenchymatous goitre, sometimes called also simple, or non-toxic goitre, is endemic in certain hilly districts in England--particularly Derbyshire and Gloucestershire--and in various parts of Scotland. It is exceedingly common in certain valleys in Switzerland. It is met with less frequently in men than in women, and it occurs chiefly during the child-bearing period of life. The toxic agent that causes goitre has been traced to certain mountain springs in goitrous districts; it has been observed that a patient with goitre may, through faecal contamination apparently, infect the water supply, and that conscripts in order to avoid military service have drunk from goitrous springs with success. Children born in a goitrous district are liable to be cretins, while if goitrous parents move to a healthy district, the children are born healthy. If the water supply of a goitrous valley be changed to a healthy spring, goitre and cretinism disappear. Thorough boiling of the water rids it of its toxic properties.
[Ill.u.s.tration: FIG. 277.--Parenchymatous Goitre in a girl aet. 15.
(Mr. D. M. Greig"s case.)]
_Morbid Anatomy._--Both the secreting and the fibrous elements share in the hyperplasia, and the gland as a whole becomes enlarged and forms a horseshoe-shaped swelling of moderate size in the neck. This swelling is soft and smooth on the surface, and is seldom quite symmetrical. In some cases the hypertrophy involves chiefly the isthmus. In others an outlying accessory lobule of thyreoid tissue const.i.tutes the bulk of the swelling, and this may extend a considerable distance from the position of the normal thyreoid, reaching even behind the sternum into the thorax--_infra-thoracic_ or _retro-sternal goitre_.
[Ill.u.s.tration: FIG. 278.--Larynx and Trachea surrounded by Goitre.]
[Ill.u.s.tration: FIG. 279.--Section of Goitre shown in Fig. 278, to ill.u.s.trate compression of Trachea.]
When the secreting elements increase out of proportion to the stroma, numerous rounded or irregular s.p.a.ces filled with a thick yellow colloid material are formed in the substance of the goitre--_colloid goitre_. The majority of these s.p.a.ces are not larger than a pea, but one or more may enlarge and form cysts of considerable size--_cystic goitre_. These varieties, especially the cystic form, attain greater dimensions than any other form of goitre.
When the fibrous stroma is greatly in excess--_fibrous goitre_--the swelling is smaller, firmer, and shows a greater tendency to contract and compress the trachea. If the sclerosis is extreme and the secretory tissue undergoes atrophy, myxdema may result.
In some cases the hyperplasia affects chiefly the blood vessels of the thyreoid--_vascular goitre_. The capillaries, veins, and arteries are increased in size and number; the swelling pulsates and increases in size when the patient makes any muscular effort. Haemorrhagic cysts may also develop in the substance of these goitres.
_Effects on the Trachea._--The trachea may be _displaced laterally_ when the enlargement of the gland affects one lobe more than the other; or it may be _compressed and narrowed_ from side to side--the _scabbard trachea_--when both lobes are about equally affected and the enlargement extends posteriorly so as almost to surround the air-pa.s.sage (Figs. 278, 279). The third effect is that of _softening of the cartilaginous rings_ of the trachea so that the air-tube, instead of having a considerable degree of elastic resiliency, is soft and flaccid and readily yields to pressure. Under these conditions an alteration in the att.i.tude of the patient, from the erect or sitting to the rec.u.mbent position, would appear to be sufficient to permit of a compression of the trachea.
Further changes in the trachea consist in catarrh and engorgement of the blood vessels of its mucous membrane, attended with an abundant secretion of mucus, which, if it acc.u.mulates behind a narrowed segment of the trachea, may still further encroach on the lumen.
_Pressure on other Structures._--The _recurrent nerve_ may be pressed upon intermittently causing spasms and choking, or continuously causing abductor paralysis and hoa.r.s.eness.
The gullet is rarely compressed; if marked difficulty in swallowing develops, some additional factor should be suspected, notably carcinoma at the junction of the pharynx with the sophagus. The carotid arteries are displaced laterally beneath the sterno-mastoids without detriment; the superficial veins--anterior and external jugular--are greatly distended in those cases in which the goitre grows downwards behind the sternum.
_Clinical Features._--The symptoms vary widely in different cases, and their severity is not proportionate to the size of the goitre. The disfigurement produced by the swelling is often the only cause of complaint. In some cases the symptoms are due to the pressure of the enlarged thyreoid on surrounding structures. In others toxic effects, in the form of cardiac, nervous, muscular, and general metabolic disturbances, predominate, and are due to absorption of excessive or abnormal thyreoid secretion. This thyreoid toxaemia varies in degree; in the milder cases it merely amounts to a nervousness or excitability that may unfit the patient for occupation; it reaches its maximum in the condition of hyperthyreoidism characteristic of exophthalmic goitre or Graves" disease (p. 614).
The skin over the goitre is freely movable, and the tumour itself can be moved transversely, carrying the larynx and trachea with it, but it cannot be moved vertically. It moves up and down with the larynx on swallowing--a point of great diagnostic value. Of the mechanical symptoms dyspna is the most constant. It may only amount to shortness of breath on exertion, or the patient may suffer from sudden and severe dyspnic attacks, especially when lying on the back during sleep, and such an attack may prove fatal. This may be due to the weight of the tumour pressing on the trachea, which has been softened and distorted by the goitre, or to temporary congestion and engorgement of the mucous membrane of the air-pa.s.sages. In these cases there is marked stridor both on inspiration and expiration, but no aphonia. In rare cases the goitre presses upon the recurrent nerve, causing spasmodic dyspna, hoa.r.s.eness, and aphonia from impaired movement of the vocal cords, and these symptoms, especially if accompanied by pain, raise the suspicion of malignancy. Disturbance of the heart"s action may cause palpitation and sudden attacks of syncope; and pressure on the blood vessels may give rise to a feeling of fullness in the head, and giddiness.
The occurrence of haemorrhage into the substance of the goitre or into a cyst, produces a sudden aggravation of the symptoms.
In _intra-thoracic_ or _retro-sternal goitre_ the tumour displaces and compresses the trachea and causes dyspna, and there are occasional paroxysmal attacks of breathlessness, which may be mistaken for asthma, particularly as the patient is usually the subject also of bronchitis and emphysema. In some cases the patient can, by a violent expiratory effort, such as coughing, project the goitre upwards into the neck. When the goitre is fixed in the thorax, the clinical features are those of a mediastinal tumour with lateral displacement of the trachea, and engorgement of the veins of the neck.
_Treatment._--The patient should change his residence to a non-goitrous district. The evidence regarding the benefit derived from the internal administration of thyreoid extract, or of preparations of phosphorus or of iodine, is conflicting.
Operative treatment is indicated when there are symptoms referable to pressure on the air-pa.s.sage, and in goitres which are steadily increasing in size. Kocher considers it advisable to operate if the patient becomes breathless on making pressure on the goitre from side to side. The suspicion of a goitre becoming malignant is also a reason for removing it by operation.
The operation--_thyreoidectomy_--consists in excising that portion of the thyreoid which is causing pressure symptoms, and this usually involves removal of one-half of the gland. The chief danger in operations for goitre is cardiac insufficiency, as evidenced by disturbed rhythm of the heart-beats, lowering of the blood pressure, or dilatation of the cavities of the heart (Kocher).