Here one encounters more difficulties than in the treatment of the adult disorder. The ventricular catheter may wander or become obstructed and require revision. Peritoneal pseudocysts may form (most shunts in children are ventriculoperitoneal). Another unexpected complication has been collapse of the ventricles, the so-called “slit ventricle” syndrome (the appearance of the ventricles on imaging studies is slit-like). This occurs more frequently in young children, although we have observed it in adults. These patients develop an intracranial low-pressure syndrome with severe generalized headaches, often with nausea and vomiting, whenever they sit up or stand. Some children become ataxic, irritable, or obtunded, or may vomit repeatedly. The CSF pressure is extremely low and the volume of CSF is much reduced. In babies, the cranium may fail to grow even though the brain is of normal size. In most shunted patients with slit ventricle syndrome, the ICP in the upright position is diminished to 30 mm H2O. To correct the condition, one would imagine that replacing the shunt valve with another that opens under a higher pressure or raising the opening pressure of an adjustable valve would suffice. Indeed, this may be successful. But once the condition is established, the most effective measure has been the placement of an antisiphon device, which prevents valve flow when the patient stands. (See further on for a discussion of intracranial hypotension in adults.)
Whether to shunt all hydrocephalic infants soon after birth is a controversial issue. In several series of cases that have been treated in this way, the number surviving with normal mental function has been small (see review of Leech and Brumback). The report of Dennis and associates is representative. They examined 78 shunted hydrocephalic children and found that 56 (72 percent) had full-scale IQs between 70 and 100; in 22 patients, the IQ was between 100 and 115; in 3 patients, it was below 70, and in 3 others, it was above 115. Mental functions improved unevenly and performance scores lagged behind verbal ones at all levels.
The use of the carbonic anhydrase inhibitor acetazolamide or other diuretics to inhibit CSF formation in children with hydrocephalus has not been successful in the hands of our colleagues, but several authors believe that by giving 250 to 500 mg of acetazolamide orally daily, shunting can be avoided in both adult normal-pressure, and infantile hydrocephalus (Aimard et al; Shinnar et al).
Usually in the context of adult hydrocephalus due to aqueductal stenosis, a rare but distinct parkinsonian syndrome occurs that may be responsive to levodopa (Zeidler). It is particularly prone to occur if there is shunted hydrocephalus and has also been a craniotomy without replacement of the bone. The syndrome usually indicates failure of the shunt. MRI sometimes shows periaqueductal and dorsal midbrain edema, including in the region of the substantia nigra (see Fig. 29-5); the mechanism of these changes is not clear. Positron emission tomography with 18FDOPA has given evidence of reduced uptake in the caudate and putamen, suggesting a functional failure of the nigrostriatal dopamine system (Racette). Shunt malfunction in children also may be heralded by upward gaze palsy (“setting-sun sign”) or even a dorsal midbrain (Parinaud) syndrome, including abnormal papillary reaction, upper lid retraction, paralysis of convergence, skew deviation, and convergence–retraction nystagmus. Shunting or shunt revision usually leads to reversal of both syndromes, but there may be a delay of days or weeks and it is often difficult to find the ideal pressure setting for the valve.