Presentation of Hydrocephalus due to Posterior Fossa Tumors in Children

Symptoms

• Elevated ICP: Most patients present with symptoms and signs of elevated ICP, which develop over several weeks or even months.
• Only rarely do patients present in extremis: With the wide availability of CT scanning and MRI, it is now rare to see children presenting with respiratory depression and coma due to acute hydrocephalus, although local geographical factors may influence this factor (patients living in remote agricultural areas or islands may not find it easy to reach medical care quickly). This rare occurrence of acute hydrocephalus is reflected in most clinical series published in the last decade.

Patterns of evolution

• Morning headaches and vomiting: After the compensating properties of a child’s nervous system to elevated ICP have been exceeded, it is a matter of few days before the definitive diagnosis. Morning nausea and vomiting with headaches that don’t resolve won’t take more than 5–7 days before it becomes apparent that the illness is something other than a viral infection. If focal signs and deficits occur (ataxia, ocular findings, torticollis), parents would be more worried and should seek medical advice promptly. On funduscopy, papilledema is commonly seen. This is caused by the increased ICP that has been present for a while before the onset of acute symptoms.

Time for evolution

The time for evolution of the symptoms and signs is related to multiple factors:

• Tumor histology: More malignant tumors usually declare their presence earlier than benign types. Tumor progression is quicker (symptom duration of weeks rather than months) and doesn’t allow compensating mechanisms to evolve.
• Tumor location: Midline tumors obstruct the CSF pathways earlier than tumors located more laterally (cerebellar hemispheres, CP angle).
• Patient’s age: Young children who don’t talk have difficulty communicating their symptoms, and a higher degree of suspicion is needed. Infants and toddlers with open fontanelles can compensate for increased ICP more easily, and this is another group for whom diagnosis can be delayed.
• Incidental diagnosis: Physical examination or imaging for other reasons (e.g., viral infections, head injuries, ophthalmological concerns) can disclose the presence of a tumor – usually benign with a different degree of hydrocephalus.

Evaluation at Presentation

• See EVALUATION

Intervention

Stabilization

• Admission for close observation: A patient who needs treatment for newly diagnosed hydrocephalus due to a posterior fossa tumor should be admitted for close observation. IV access and NPO orders follow. If the patient’s condition deteriorates rapidly, emergency intubation and transfer to the ICU should follow.
• Fluids: Fluid administration and control of emesis with medication are used, and most neurosurgeons would commence dexamethasone.
• Imaging: Prior to any neurosurgical intervention, a good quality scan is mandatory, with consideration taken of the clinical status.
• Guard against upward herniation if treating hydrocephalus before tumor: If the next option is treatment only of the hydrocephalus, it is paramount to consider upward herniation and avoid excess CSF loss upon entrance into the ventricles. CSF samples are sent for microbiology and cytology. If an endoscope is used, inspection of the ventricles is important for intraventricular metastases and possible biopsies.

Preparation for definitive intervention, non-emergent

• Imaging: If there is time, a detailed MRI investigation precedes intervention. Imaging can include head and spine scans with and without contrast, MR spectroscopy, CSF flow studies and volumetric scan for navigation. The anatomy of the third ventricle (e.g., bulging floor) and the position of the basilar artery are important if an ETV is considered. Further tumor features are examined if the definitive plan is tumor resection (position, size, morphology, enhancement, necrosis, cysts, relationship to surrounding structures).

Preparation for definitive intervention, emergent

• ETV: A patient who is critically ill usually is treated for the hydrocephalus alone if time doesn’t allow for tumor resection. In experienced pediatric centers an ETV procedure could be performed any time, even on an emergency basis. Again, upward herniation should always be considered in these cases. If only a CT scan is available and there is no time for MRI, most surgeons would avoid an ETV.
• EVD or shunt: The other options are EVD and ventriculoperitoneal shunt. Most would choose an EVD for a couple of days, before definitive treatment with tumor resection. There is significant risk for CSF infection, especially with prolonged drainage. A ventriculoperitoneal shunt with high setting of the valve is a less preferable option. Some surgeons are skeptical because of possible seeding of the peritoneum with tumor cells (not proved), but most wouldn’t like hardware implantation and shunt dependencies with the known problems.

Admission Orders

• HOB, positioning, and activity: The head of the bed should be at 30–45 degrees. Supine position is preferred if the patient can tolerate it. Normal activity may proceed as tolerated. Walking unattended should be avoided if ataxia exists due to the increased risk of falls.
• VS: On admission the patient is monitored continuously (HR, SatO2, BP, ECG). Posterior fossa lesions can cause HR and BP abnormalities (bradycardia, hypertension), so close attention is necessary.
• IVF and rate: NaCl 0.9% + 20 mEq/l KCl or NaCl 0.45%. Rate: 4 ml/kg for first 10 kg, 2 ml/kg for second 10 kg, and 1 ml /kg for each subsequent Kg (15).
• CSF drainage parameters: If EVD is used prior to tumor resection, it is paramount to avoid excessive CSF loss due to upward tentorial herniation risk. An initial setting at 20–30 cmH2O with gradual decrease is used by some neurosurgeons. Others start at 15–20 cmH2O with special care taken that the hourly drainage does not exceed 5–10 ml CSF (36).