Another medical sign, in infants, is a characteristic fixed downward gaze with whites of the eyes showing above the iris, as though the infant were trying to examine its own lower eyelids.The elevated ICP may cause compression of the brain, leading to brain damage and other complications. A complication often overlooked is the possibility of hearing loss due to ICP. The mechanism of ICP on hearing loss is presumed that the transmission of CSF pressure to and from the Perilymphatic space through a patent cochlear aqueduct. The cochlear aqueduct connects the Perilymphatic space of the inner ear with the subarachnoid space of the posterior cranial fossa. A loss of CSF pressure can induce Perilymphatic loss or endolymphatic hydrops resembling the clinical presentation of Ménières disease associated hearing loss in the low frequencies.CSF can accumulate within the ventricles, this condition is called internal hydrocephalus and may result in increased CSF pressure. The production of CSF continues, even when the passages that normally allow it to exit the brain are blocked. Consequently, fluid builds inside the brain, causing pressure that dilates the ventricles and compresses the nervous tissue. Compression of the nervous tissue usually results in irreversible brain damage. If the skull bones are not completely ossified when the hydrocephalus occurs, the pressure may also severely enlarge the head. The cerebral aqueduct may be blocked at the time of birth or may become blocked later in life because of a tumor growing in the brainstem.
Scarring and fibrosis of the subarachnoid space following infectious, inflammatory, or hemorrhagic events can also prevent reabsorption of CSF, causing diffuse ventricular dilatation. Noncommunicating
Noncommunicating hydrocephalus, or obstructive hydrocephalus, is caused by an obstruction to the flow of CSF. Foramen of Monro obstruction may lead to dilation of one, or if large enough (e.g., in colloid cyst), both lateral ventricles. The aqueduct of Sylvius, normally narrow, may be obstructed by a number of genetic or acquired lesions (e.g., atresia, ependymitis, hemorrhage, or tumor) and lead to dilation of both lateral ventricles, as well as the third ventricle. Fourth ventricle obstruction leads to dilatation of the aqueduct, as well as the lateral and third ventricles (e.g., Chiari malformation). The foramina of Luschka and foramen of Magendie may be obstructed due to congenital malformation (e.g., Dandy–Walker malformation). Other
Normal pressure hydrocephalus (NPH) is a particular form of chronic communicating hydrocephalus, characterized by enlarged cerebral ventricles, with only intermittently elevated cerebrospinal fluid pressure. Characteristic triad of symptoms are; dementia, apraxic gait and urinary incontinence. The diagnosis of NPH can be established only with the help of continuous intraventricular pressure recordings (over 24 hours or even longer), since more often than not instant measurements yield normal pressure values. Dynamic compliance studies may be also helpful. Altered compliance (elasticity) of the ventricular walls, as well as increased viscosity of the cerebrospinal fluid, may play a role in the pathogenesis.