55 Slit Ventricle Syndrome

Jeffrey Atkinson

Fig. 55.1 Computed tomography scan of the brain revealing relatively small lateral ventricles and ventriculoperitoneal shunt located within the ventricle.

Clinical Presentation

A 15-year-old girl with a history of myelomeningocele repaired at birth and with a ventriculoperitoneal (VP) shunted inserted shortly after birth presents with headache.

She has a history of only one previous shunt revision.

She is stable neurologically with a L4/L5 clinical level (both motor and sensory deficits), but presents with a new onset of disabling headaches over the past several months.

Computed tomography (CT) scan shown in Fig. 55.1 is no different from the routine scan done 1 year previously when she was completely asymptomatic.

Questions

What is the differential diagnosis?
What is the next possible step in the workup of this patient?

Shunt revision is performed, and at the time of surgery the distal and proximal catheters are changed due to “sluggish” flow. She is relieved of her headaches for a few hours, but the symptoms return shortly thereafter.
What are the diagnostic possibilities now?
What is the next step in her management?

CT scan remains unchanged; nuclear medicine shuntogram shows good flow.
What are other potential investigations?

Intracranial pressure (ICP) monitoring shows readings generally between 5 and 15 mm Hg depending on her position with no single reading higher than 20 mm Hg, and no reading lower than –5 mm Hg.
Describe the different types of syndromes associated with headaches and stable ventricle size on CT scan and outline management strategies for each.

Answers

What is the differential diagnosis?

Headache of the usual types (tension, migraine, etc.)
Headache related to shunt malfunction
Headache related to overshunting
It is essential to consider shunt malfunction even in the presence of unchanged or small ventricles. It may be of benefit to know the details of her last shunt revision with respect to headache history and changes seen on CT scan.

What is the next possible step in the workup of this patient?

Diagnostic tests should first focus on establishing whether or not there is normal shunt function.

There are several strategies in this regard:

Ophthalmology consultation might demonstrate papilledema missed on routine clinical exam.

In the absence of this finding, this patient is not acutely ill and might be watched expectantly with migraine medication.

However, with this strategy, lack of improvement in symptoms must provoke another look at the shunt.

Repeat CT scan after 24 to 48 hours might show some change in ventricle size.

Nuclear medicine shuntogram may be of some value. This test will include a shunt tap, which is a measure, though poor, of ICP at one moment in time. With good proximal reflux into the ventricle as an essential component of a normal test, some groups have reported this to be a reliable marker for shunt dysfunction.1

ICP monitoring over 24 to 48 hours may give an idea about the headache pattern and ICP management, which might prompt shunt or valve revision.

Finally, a semielective shunt exploration might demonstrate a poorly working component that could be replaced.²
What are the diagnostic possibilities now?
- Early return of symptoms after shunt revision always prompts an appropriate workup for shunt malfunction.
- A surgery can always convert a working shunt to a nonworking shunt. In the absence of any new signs of shunt malfunction, the same diagnostic possibilities as stated previously apply.
What is the next step in her management?
- This patient needs an early-repeat CT scan.
- If there is still no change in her ventricles, the management could proceed according to Question #2.
What are other potential investigations?
- At this stage, ICP monitoring becomes the best option.
Describe the different types of syndromes associated with headaches and stable ventricle size on CT scan and outline management strategies for each.
- Patients with VP shunts, new headaches, and no change in ventricular size on their CT scan can be broken down into four categories (variably described as part of the “slit ventricle syndrome”):
  - Shunt is malfunctioning despite CT findings – this can be determined by a shuntogram or shunt exploration, and the treatment is shunt revision.³
  - Shunt is overdraining – ICP monitoring may be necessary, though clinical history can be helpful and upgrading of valve to a higher resistance setting would be the appropriate treatment.^3,4
  - Shunt is functioning maximally, but ICP is high anyway – this is rare and can only be really established with shunt exploration and ICP monitoring. In this rare instance, cranial expansion procedures would be the treatment of choice.³
  - Not a shunt problem – established with normal ICP tracing with ICP monitor, and treatment is neurology and/or pain service consultation, and other medical management for chronic headache relief.²