If the hydrocephalus is arrested, the infant or child is usually developmentally delayed in motor function but often surprisingly verbal. In extreme circumstances, the head may be so large that the child cannot hold it up and must remain in bed. If the head is only moderately enlarged, the child may be able to sit but not stand, or stand but not walk. Acute exacerbations of hydrocephalus or a febrile illness may cause vomiting, stupor, or coma.
The special features of congenital hydrocephalus associated with the Chiari malformation, aqueductal atresia and stenosis, and the Dandy-Walker syndrome are discussed in Chap. 37. Also mentioned here is a rare condition termed “bobble head” syndrome that is caused by a suprachiasmatic arachnoid cyst or by third ventricular enlargement, as discussed in Chap. 30. These lesions cause the child’s head to move forward and backward or side-to-side constantly or intermittently at about 2 to 3 Hz. There is no direct connection to another rhythmic head movement, spasmus nutans (listed in some books as “mutans”), or to seesaw nystagmus described in Chap. 13, but the location of the causative lesions, in and adjacent to the third ventricle, is similar in all of them.
Here, the ventricular enlargement becomes evident only after the cranial sutures have closed (Fig. 29-3). The causes of obstruction to the flow of CSF are diverse, and although some are clearly congenital, symptoms may be delayed as late as adolescence, or early adult life, or even later. In some instances, the condition gives rise to normal-pressure hydrocephalus, as discussed below and in Chap. 6. The clinical features of occult hydrocephalus and the course of the illness are quite variable. We have seen a few cases in adults in whom the gait disturbance from congenital aqueductal stenosis appeared abruptly enough to give the impression of a cerebellar or frontal stroke. For unexplained reasons, the symptoms of previously occult hydrocephalus may also appear abruptly after minor cranial trauma. A suck reflex and grasp reflexes of the hands and feet are variably present; plantar reflexes are sometimes extensor. Last, there may be urinary urgency leading to sphincteric incontinence, often without the patient’s awareness.
Chapter 30 discusses occult hydrocephalus caused by intracranial tumor growth.
Surprisingly, little has been written about this condition despite its frequency in clinical practice. It is seen most often following subarachnoid hemorrhage from a ruptured aneurysm, less often with bleeding from an arteriovenous malformation or from deep intracerebral hemorrhage that dissects into the ventricles. It may also occur as the result of obstruction of the CSF pathways in the fourth ventricle by a tumor or cerebellar–brainstem hemorrhage, or within the basal cisterns by neoplastic infiltration of the meninges, although this last process tends to evolve more subacutely. The patient complains of a headache of varying severity and may have visual obscuration, vomiting, and then becomes drowsy or stuporous over a period of minutes or hours. Bilateral Babinski signs are found, and in advanced stages, which are associated with coma, there is increased tone in the lower limbs and extensor posturing. Early in the process, the pupils are normal in size and the eyes may rove horizontally; as the ventricles continue to enlarge, the pupils become miotic, the eyes then cease roving and assume an aligned forward position, or there may be bilateral abducens palsies and limitation of upward gaze. The speed with which hydrocephalus develops determines whether there is accompanying papilledema.