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_--passes 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 oesophagus, so that it moves with these structures on
swallowing. In this capsule are numerous veins; and in the groove
between the oesophagus 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-albumin--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 myxoedema, 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 puberty, 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 oesophagus 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 dyspnoea.
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-passage or the oesophagus.
_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.
[Illustration: 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
constitutes 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_.
[Illustration: FIG. 278.--Larynx and Trachea surrounded by Goitre.]
[Illustration: FIG. 279.--Section of Goitre shown in Fig. 278, to
illustrate compression of Trachea.]
When the secreting elements increase out of proportion to the stroma,
numerous rounded or irregular spaces filled with a thick yellow
colloid material are formed in the substance of the goitre--_colloid
goitre_. The majority of these spaces 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, myxoedema 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-passage (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 attitude of the patient, from the erect or sitting
to the recumbent 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 accumulates 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 hoarseness.
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 oesophagus. 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 dyspnoea is the most constant. It may only amount to
shortness of breath on exertion, or the patient may suffer from sudden
and severe dyspnoeic 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-passages. 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 dyspnoea, hoarseness, 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 dyspnoea, 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-passage, 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).
It is sometimes advisable to perform the operation under local
anaesthesia. A general anaesthetic is, however, preferred in this
country. The injection of 1/6th grain of morphin and 1/120th grain of
atropin half an hour before the operation, and the administration of
ether by the open method, or by intra-tracheal insufflation, is safe
and satisfactory.
There is reason to believe that the absorption of thyreoid secretion
squeezed from the divided surfaces gives rise to a condition known as
_acute thyreodism_ during the first few hours after operation; its
symptoms are elevation of temperature, increase in the pulse-rate
(150-200), rapid respiration with dyspnoea, flushing of the face,
muscular twitchings, and mental excitement. The gentle handling of the
tumour and the employment of a drainage tube for the first forty-eight
hours diminishes this risk.
_Tetany_, as evidenced by the occurrence of cramp-like contractions of
the thumb and fingers, may supervene within a few days of the
operation if one or more of the para-thyreoids have been inadvertently
removed. It may be controlled by large doses of calcium lactate. On no
account may the whole of the thyreoid gland be removed, as this is
followed by the development of symptoms closely resembling those of
myxoedema--_operative myxoedema_ or _cachexia strumipriva_.
_Treatment of Sudden Dyspnoea._--When dyspnoea suddenly supervenes and
threatens life, it is sometimes possible to relieve the pressure on
the trachea by open division of the skin, superficial fascia, platysma
and deep fascia in the middle line of the neck, so as to relax the
tension on the goitre. If this is insufficient, the isthmus may be
divided. Should relief not follow, tracheotomy must be performed, and
a long tube or a large-sized gum-elastic catheter with a terminal
aperture be passed along the trachea beyond the seat of obstruction.
#Adenoma of the Thyreoid.#--In this condition the swelling of the
thyreoid is due to the growth within its substance of one or more
adenomas of variable size and surrounded by a capsule. The rest of
the gland may be normal, or may show some degree of hyperplasia. Some
are solid, others undergo cystic degeneration, the glandular tissue
being replaced by a quantity of clear or yellowish fluid, sometimes
mixed with blood. The cysts thus formed may be unilocular or
multilocular, and intra-cystic papillary vegetations frequently grow
from their walls. The walls of the cysts may be thin, soft, and
flaccid, or thick and firm, or they may even be calcified.
The thyreoid is enlarged, but instead of the uniform enlargement which
characterises the parenchymatous goitre, it tends to be uneven, with
hillocky projections corresponding to the individual cysts (Fig. 280),
and in these fluctuation may be detected. It is to be noted that
there are no toxic symptoms in cystic adenoma.
[Illustration: FIG. 280.--Multiple Adenomata of Thyreoid in a woman
aet. 50.
(Mr. D. M. Greig's case.)]
[Illustration: FIG. 281.--Cyst of Left Lobe of Thyreoid.
(Mr. D. M. Greig's case.)]
The treatment is necessarily operative; cystic tumours may be tapped
and injected with iodine, but the more satisfactory procedure, both
with the solid and cystic forms, is to incise freely the overlying
thyreoid tissue and enucleate the tumour.
#Malignant Disease of the Thyreoid.#--This, whether in the form of
_carcinoma_ or _sarcoma_, usually develops in a gland that has been
the seat of goitre for several years, although it may begin in a
previously healthy gland.
_Clinical Features._--Both sexes, above the age of fifty, are affected
in about equal proportion. The characteristic features are that the
tumour undergoes a progressive increase in size, that it becomes fixed
to its surroundings, that its surface tends to be uneven and nodular,
and its consistence densely hard. The voice often becomes hoarse from
abductor paralysis due to infiltration by the growth, usually of the
left recurrent nerve. The effects upon the trachea are more decided
and more progressive than in parenchymatous goitre; it displaces and
compresses the trachea and frequently overlaps it, so as to bury the
air-passage completely. If the tumour tissue has actually penetrated
the trachea, the expectoration is tinged with blood. Dysphagia is
rarely a prominent symptom. The lymph glands become enlarged after the
tumour bursts through the capsule; and metastases to the lungs and
bones, particularly the skull, sternum, and mandible, are common. When
the goitre extends behind the sternum--the _malignant form of
retro-sternal goitre_--the pressure symptoms are due to the
encroachment upon the limited accommodation of the upper opening of
the thorax; the trachea especially suffers, and the pressure on the
veins causes distension of the anterior and external jugulars and
their tributaries. The patient is unable to lie down; there are
violent paroxysms of coughing, and an abundant frothy expectoration.
Death may take place suddenly from asphyxia, from heart failure, or
from displacement of a thrombus from one of the veins in the neck.
_Treatment._--It is only in the earliest stages that a malignant
goitre can be successfully removed. In the later stages complete
extirpation is not to be attempted, as it usually involves the removal
of a portion of the trachea or oesophagus, and the operation is
attended with grave risk to life.
Operative interference is often called for, however, for the relief of
respiratory embarrassment. _Tracheotomy_ may prove a difficult and
dangerous procedure, owing to the trachea being buried under the
goitre and displaced or narrowed by it, so that it is not easy to
reach it or to introduce an efficient tube beyond the point of
obstruction. A more certain method consists in exposing the goitre by
an incision as for thyreoidectomy, rapidly removing sufficient of the
growth to expose the trachea and admit of a tube being introduced. If
there is a retro-sternal prolongation compressing the trachea within
the thorax, a long flexible tube may have to be passed beyond the site
of the compression before the dyspnoea is relieved. The benefit is
immediate and decided; the accumulated secretion is coughed up, and
after a few deep breaths the patient is able to lie down, and usually
falls asleep. The stridor disappears. Unfortunately the relief is
only temporary, and the patient soon succumbs to a broncho-pneumonia,
or to secondary haemorrhage from the trachea.
#Toxic Goitre#--#Exophthalmic Goitre#--#Graves'# or #Basedow's
Disease#.--These terms are applied to a variety of goitre
in which the symptoms due to absorption of thyreoid
secretion--_thyreotoxicosis_--predominate. The name "exophthalmic
goitre" is misleading, as in some cases the enlargement of the
thyreoid, and in others the eye symptoms, are scarcely appreciable,
while the general symptoms are well marked. The term toxic goitre or
_hyperthyreoidism_, suggested by C. H. Mayo, is preferable, as the
manifestations of the disease depend upon excessive or abnormal action
of the thyreoid tissue.
[Illustration: FIG. 282.--Exophthalmic Goitre.]
The condition is chiefly met with in young adult women, and may
develop suddenly after a shock to the nervous system. The intoxication
affects the higher cerebral functions and causes nervousness,
irritability, and tremor; the cardiac and vaso-motor centres, causing
tachycardia and pallor of the skin; the sympathetic fibres to the eye,
causing protrusion of the eyeballs, staring of the eyes without
winking, narrowing of the palpebral fissure, dilatation of the pupil,
and lagging behind of the upper lid, and sometimes also of the lower
lid--von Graefe's symptom. There may be diarrhoea and vomiting, loss
of weight, and in the worst cases there is delirium at night. In
course of time there develops cardiac insufficiency with fibroid
degeneration of the myocardium. Coagulation of the blood is retarded,
and there is a marked diminution in the number of leucocytes,
especially the neutrophils, and an increase in the lymphocytes
(Kocher).
In the early stages the thyreoid is enlarged and pulsatile, and bruits
may be heard over it; later, these vascular symptoms disappear, and
only a firm, diffuse, uniform swelling implicating all parts of the
gland remains.
_Prognosis._--The tenure of life is uncertain as the patient offers
little resistance to intercurrent affections such as influenza and
pneumonia. If the average course of the disease is represented by a
curve, the greatest height is reached during the second half of the
first year and then descends. For the next two to four years it
fluctuates with occasional exacerbations of symptoms due to fright or
worry.
_Treatment._--Medical measures, along with the external application of
radium, the strict observance of rest in bed with the exclusion of all
forms of excitement and worry, the administration of bromides, heroin
or other sedatives, and of digitalis or other cardiac tonics, are to
be prescribed in the first instance, and in any case, as a desirable
preparation for operation.
_Operative measures_ consist in the _ligation_ of the vessels and
nerves at one or other pole of the gland--usually the superior on one
side--followed by, if necessary, a partial _thyreoidectomy_.
Crile of Cleveland has organised his clinic in the direction of
arranging that the operation shall be performed without the patient
knowing that it is to take place--what he calls "stealing the
goitre"--the thorough preparation of the patient for the operation,
the minimising the risk from the anaesthetic by the combination of
novocain locally and of nitrous oxide and oxygen; and of diminishing
the risk of absorption of thyreoid secretion by packing the (open)
wound with gauze wrung out of a solution of flavin.
Operations on the cervical sympathetic cord have been abandoned.
The presence of toxic goitre may influence the question of operation
in the treatment of other surgical conditions, and may determine the
selection of one or other form of anaesthesia.