Hydrocephalus is a condition in which there is an increase in the amount of cerebrospinal fluid in the skull and an enlargement of the ventricular system or the subarachnoid space due to cranio-cerebral disorders that result in excessive secretion or impaired circulation and absorption of cerebrospinal fluid. The broad definition of hydrocephalus should also include subarachnoid fluid and subdural fluid.
Classification according to pathology
(1) Obstructive hydrocephalus: Obstructive hydrocephalus, also known as non-traffic hydrocephalus or intracerebroventricular type obstructive hydrocephalus, is formed when the lesion is located in or near the ventricular system and obstructs the cerebrospinal fluid circulation in the ventricular system. It is the most common type of hydrocephalus, which is caused by obstruction above the fourth ventricular outlet. It is common in arachnoid cysts, atresia or stenosis of the aqueduct, hypoplasia of the median foramen or interventricular foramen, Chiari malformation, craniopharyngioma, etc.
(2) Traffic hydrocephalus: Traffic hydrocephalus is hydrocephalus due to obstruction of the extraventricular cerebrospinal fluid circulation pathway or impaired absorption, or hydrocephalus due to excessive production of cerebrospinal fluid.
Clinical manifestations
Typical symptoms are headache, vomiting, blurred vision, optic nerve papillary edema, occasional diplopia, vertigo and seizures. Some patients have slow pulse, elevated blood pressure, respiratory disturbances, and pupillary changes; some patients may have oculomotor disorders, cone bundle signs, changes in muscle tone and meningeal irritation signs; some show internal distension syndrome, such as vomiting, constipation, gastrointestinal bleeding, neurogenic pulmonary edema, uremia, cerebral sodium retention, and cerebral salt depletion syndrome.
Clinical features of hydrocephalus in infants and children
(1) Increase in head circumference The infant’s head enlarges progressively within a few weeks or months after birth, and the fontanelle enlarges and bulges with it. The growth ratio of the head to the trunk is disproportionate, such as the head is too large and heavy and hangs down in front of the chest, the head is not proportional to the face, the head is large and small, the forehead is prominent, the jaw is sharp and thin, the skull is thin, and there is also superficial venous anger, and the scalp is shiny.
(2) Enlarged fontanelle and increased tension When the child is held vertically and quietly, the fontanelle is still bulging and not sunken, and no normal pulsation can be seen, it indicates increased intracranial pressure. The main manifestation of increased intracranial pressure in infancy is vomiting, and since infants cannot speak yet, they often express head discomfort and pain by scratching their heads, shaking their heads, crying, etc. When the condition worsens, drowsiness or lethargy may appear.
(3) Sound of broken cans When percussing the head of a child with hydrocephalus (at the junction of frontal-temporal-parietal lobe), the sound is like percussing a broken can or a ripe watermelon.
(4) “Sunset eyes” phenomenon The further development of hydrocephalus, compression of the parietal part of the midbrain or due to the axial displacement of the brainstem, produces a syndrome similar to Parinaud’s oculomotor paralysis, that is, paralysis of the upper gaze, so that the infant’s eyes cannot look upward, and the so-called “sunset eyes” sign appears. “(5) cranial transillumination
(5) cranial transillumination severe hydrocephalus if the thickness of brain tissue (cortical, white matter) is less than 1cm, direct contact with the scalp with a strong flashlight, such as transillumination with brightness is positive, such as normal brain tissue is negative (no brightness).
(6) Optic nerve papillary atrophy Primary optic nerve atrophy is more common in infantile hydrocephalus, and optic nerve papillary edema is not seen even with increased intracranial pressure.
(7) Neurological dysfunction VI paralysis of the cranial nerves often prevents the infant’s eyes from abducting. The progressive enlargement of the ventricular system causes significant cerebral atrophy in most cases. In the early stages, neurological function is still well maintained, but in the later stages, conus pallidus, spastic paralysis, and denervation tonicity may appear, and intellectual development is significantly worse than that of normal infants of the same age.
Children with hydrocephalus often have other deformities, such as spina bifida, inward slanting of the eye (due to spinal nerve palsy), increased muscle tone in both lower limbs, hyperactive knee tendon reflexes, developmental delays or severe malnutrition.
Clinical features of hydrocephalus in older children and adults
(1) Clinical manifestations are generally headache, nausea, vomiting, and visual impairment.
(2) Patients with chronic hydrocephalus are clinically characterized by chronic intracranial pressure increase, which may present with bilateral temporal or whole cranial pain, nausea, vomiting, optic nerve papillary edema or optic nerve atrophy, intellectual developmental impairment, motor dysfunction, etc.
(3) Normal pressure hydrocephalus is a special type of traffic hydrocephalus, mostly occurring at the base of chronic traffic hydrocephalus, where compensatory regulation results in reduced secretion and accelerated compensatory absorption of partially intact arachnoid granules, resulting in a new equilibrium. Although the ventricular system is enlarged, the cerebrospinal fluid pressure is normal or close to normal, so it is called normal pressure hydrocephalus. CT manifestations: general enlargement of the ventricular system and deepening of the cerebral sulcus, but the two are disproportionate, with more significant enlargement of the ventricles. Clinical manifestations are mostly dementia, ataxia, and urinary incontinence (triad of signs), which should be differentiated from cerebral atrophy.
Diagnostic clinical features
Chronic obstructive hydrocephalus in adults often presents with intermittent headache, head swelling, head sinking, dizziness, tinnitus and ear blockage, loss of vision, and weakness of lower limbs; in infants and children, obstructive hydrocephalus mostly presents with enlarged skull, tense and full fontanelle, open cranial sutures, angry scalp veins, sunset eyes, nystagmus, strabismus, and may be accompanied by speech and motor dysfunction, convulsions, and mental retardation.
Imaging features
The CT sign is ventricular enlargement. Moderate and severe hydrocephalus can be diagnosed with a single scan, while mild cases require multiple observations to confirm progressive ventricular enlargement for diagnosis. There are three signs of obstructive hydrocephalus on CT: round enlargement of the superior lateral frontal horn; enlargement of the temporal horn; and periventricular hypointensity.
Differential diagnosis of subdural hematoma or effusion in infants
Although infants with subdural hematoma or effusion also have cranial enlargement and cranial thinning, they are often accompanied by optic nerve papillary edema but lack the sunset sign. CT scans can be used to differentiate.
Rickets
In rickets, the skull is irregularly thickened, resulting in protrusion of the frontal and occipital bones, a square cranium, and what appears to be an enlarged skull without symptoms of increased intracranial pressure or ventricular enlargement, but with generalized skeletal abnormalities.
Cerebral hypoplasia
Although the ventricles are enlarged, the head is not large and does not show intracranial pressure increase, but has neurological and intellectual developmental disorders.
Hydrocephalic anencephaly
In addition to the absence of cerebral cortex in the occipital region, a prominent basal ganglion is also seen on CT films.
Macrocephaly
Although the skull is large, there are no symptoms of increased intracranial pressure and the ventricles are normal in size on CT.
Cerebral atrophy
It is mainly distinguished from normal pressure hydrocephalus. The symptoms are similar, but cerebral atrophy usually develops after the age of 50 years and the symptoms progress slowly over several years. CT examination is characterized by mild enlargement of the ventricles without accumulation of the fourth ventricle and significant widening of the sulcus. MRI shows enlargement of both the ventricles and the subarachnoid space.
Non-surgical treatment
It is indicated for early or mild disease with slow progression, and aims to reduce the secretion of cerebrospinal fluid or increase the body’s water discharge by
A: Application of diuretics, such as acetazolamide, dihydroketorol, tachyphylaxis, mannitol, etc.
B: Repeated puncture and release of fluid through fontanel or lumbar spine.
Surgical treatment
Surgical treatment is indicated for cases with high intracerebroventricular pressure (more than 250 mm water column) or failure by non-surgical treatment. Severe hydrocephalus such as head circumference over 50 cm, cortical atrophy thickness below 1 cm, has been combined with serious functional impairment and deformity, can also be treated surgically but the surgical efficacy is not good.