The clinical manifestations of the insufficiency of function of the
parathyroid glands is well understood. This came about through the
study of endemic tetany, and, especially, noting that tetany followed
operations when the entire thyroid gland was removed. Considerable
experimental work on animals was next in order, until the discovery
was made that the thyroid gland and parathyroids are anatomically
independent, and that tetany is entirely dependent upon the loss
of function of the parathyroid glands. =Operative tetany= is now
comparatively rare, since the surgeon is particularly careful not to
injure the parathyroids in his operations on goiters, though mild forms
may occur through damage of the tissues or extension of inflammatory
processes.
There are =other forms= of tetany aside from operative, that occur in
both adults and children, but instability and insufficiency of the
function of the glands are basic to all cases. This is the common
factor, which may be modified by tissue resistance and various hygienic
factors.
In tetany there are paroxysmal, and often painful, contractions of the
muscles of the extremities. Both sides are affected, and occasionally
the spasms may extend to other muscles of the body. This is due to an
abnormal excitability of the nervous system. Probably the secretion of
the parathyroids have normally a restraining effect upon the nervous
impulses, which when removed, or insufficient, or possibly perverted,
results in the tonic spasms.
Thus the =predisposing condition= of tetany may be either =acquired=
or =congenital=. Children may be born with defective parathyroids. In
such instances there is probably a hypoplasia of tissue, which may
markedly vary in a series of cases, and give rise to different degrees
of tetany. Other factors, nutritional and toxic, would, very likely, be
important exciting causes. Hemorrhages and fibrosis have been noted in
some cases, that add to the injury of the tissues.
The blood and nerve tissues in tetany show a decreased amount of
=calcium=. It is claimed by some that the abnormal excitability of the
nervous system is due to the lack of calcium. Noel Paton[113] believes
that, though this may bear some relationship, the parathyroids control
the metabolism of =guanidine=, and that guanidine intoxication is the
cause of the symptoms. Guanidine seems to regulate the tone of the
skeletal muscles, and is closely related to urea.
Tetany may occur under many conditions: during pregnancy and nursing,
the infectious and nutritional diseases, the diseases of the thyroid
and very often gastro-intestinal disorders. There are various exciting
causes, such as cold, worry, overfatigue, etc. Alcohol, ergot,
morphine, chloroform, and other poisoning may precipitate an attack.
But in all these cases the parathyroids are previously damaged.
The blood supply to the glands is from branches supplying the thyroid
organ. This intimacy implies that the same sympathetic nerves to the
thyroid vessels are in control. Probably there are distinct secretory
nerves, as well as vasomotors, that are connected with the upper dorsal
and cervical sympathetics. =Lesions= related to the corresponding
spinal areas probably affect the integrity of the parathyroid function.
Schafer says: “The parathyroids are amongst the most vascular organs
in the body. They are supplied each by a special branch of the
inferior thyroid artery. The sinus-like capillaries come into close
relationship with the epithelial cells of the gland. The nerves of the
parathyroids, like those of the thyroids, pass both to the vessels and
to the secreting cells. Some evidence has been adduced which seems to
show that the cell-activity is controlled by the nervous system.”
Hence it would seem that in many cases of tetany, aside from those
cases due to operative injury and possibly certain congenital
instances, =osteopathic lesions= affecting the nerve and vascular
supply of the organs may so lessen, or pervert, the secreting cells
that tetanic states may supervene, especially where lowered nutrition,
toxins, and infections are inciting factors.
=Symptoms.=—The tonic contraction of the muscles may last a few minutes
or may persist for several hours, and are usually confined to the hands
and feet. The fingers and toes are first affected by the spasm, which
extends upward toward elbows and knees. This is commonly preceded by
numbness and more or less pain in the parts. Occasionally there is a
general ill-feeling, depression, and headache. There may be rise of
temperature, and some edema of the affected parts. There are no mental
symptoms.
The fingers are partly flexed at the metacarpo-phalangeal joints and
rigidly extended at the inter-phalangeal joints, the thumb is markedly
adducted and the fingers drawn close together. The wrist may be flexed,
and in severe cases the elbows flexed and adducted. When the feet are
contracted the toes are drawn together, flexed, and may overlap, and
the feet are arched.
=Trousseau’s phenomenon.=—The spasm is increased by pressure over the
median or ulnar nerves, or blood-vessels supplying the parts. This may
also excite an attack. =Chvostek’s phenomenon.=—Percussion over the
facial nerve will cause quick contraction of the muscles innervated.
=Erb’s phenomenon.=—The electrical excitability of the motor nerves is
markedly increased.
=Diagnosis.=—The characteristic attitude, and the irritability of the
motor and sensory nerves, make diagnosis easy. It may be confused
with =meningitis=, but in tetany there are no brain symptoms, while
in meningitis there are no characteristic signs of tetany. Generally,
there is little probability of confusing the disease with =tetanus=, or
=hysteria=.
=Treatment.=—Most cases are of a mild type, and recovery is the rule.
A great deal depends upon the underlying cause. Malnutrition, if long
continued, is a very important factor that may readily predispose to
the disorder. Rickets in children is often a basic consideration.
Rest, warm baths, and careful inhibitory relaxation of the tissues
materially assist in controlling the spasms. Attention to the thyroid
innervation should not be neglected. In indicated cases thyroid feeding
may be of assistance. The diet is of special importance, for many cases
present some disorder of the gastro-intestinal tract. Meat should not
be given. Milk is of great value, owing to its calcium content. The
administration of calcium is highly recommended, for reasons stated
under etiology.