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CSF Shunts and Complications


KEY FACTS

Terminology

  • Hydrocephalus

    • Enlargement of cerebral ventricles secondary to abnormal cerebrospinal fluid (CSF) formation, flow, or absorption resulting in ↑ CSF volume

Imaging

  • Shunt failure → dilated ventricles + edema around ventricles, along catheter and reservoir

  • Use CT or MR to evaluate ventricle size, plain radiograph shunt series to identify mechanical shunt failure

  • Baseline CT/MR following shunt insertion, follow-up at 1 year and as clinically needed

  • Shunt radionuclide studies: Used to confirm distal obstruction

Top Differential Diagnoses

  • Shunt failure with normal ventricle size or lack of interstitial edema

  • Noncompliant (“slit”) ventricle syndrome

  • Intracranial hypotension, low pressure syndromes

Pathology

  • Obstructive hydrocephalus: Secondary to physical blockage by tumor, adhesions, cyst

  • Communicating hydrocephalus: Secondary to ↓ CSF absorption across arachnoid granulations

Clinical Issues

  • Older children/adults: Headache, vomiting, lethargy, seizure, neurocognitive symptoms

  • Infants: Bulging fontanelle, ↑ head circumference, irritability, lethargy

Diagnostic Checklist

  • Shunt + headache not always shunt failure

  • Confirm programmable shunt valve setting after MR

  • Compare current CT with prior studies to detect subtle changes in ventricle size

Lateral skull radiograph of acute ventriculoperitoneal shunt failure from a plain radiograph shunt series demonstrates a mechanical shunt catheter disconnection
between the programmable valve and the reservoir.

Axial bone CT in the same patient reveals the mechanical catheter disconnection
between the reservoir and the programmable shunt valve. This finding had not appeared on the most recent comparison CT scan (not shown).

Axial NECT in a patient with acute ventriculoperitoneal (VP) shunt failure shows symmetric periventricular interstitial edema
within the deep white matter. The ventricles were larger than on prior CTs (not shown).

Axial NECT in a patient with VP shunt
who presented with severe headaches shows collapsed lateral ventricles
. Slit ventricle syndrome presents as severe headaches due to noncompliant ventricles and should not be confused with radiological slit ventricles.

TERMINOLOGY

Abbreviations

  • Shunt types: Ventriculoperitoneal (VP), ventriculoatrial (VA), ventriculopleural (VPL), lumboperitoneal (LP)

Definitions

  • Ventriculomegaly

    • General term for enlargement of cerebral ventricles

  • Hydrocephalus (HCP)

    • Enlargement of cerebral ventricles secondary to abnormal CSF formation, flow, or absorption resulting in ↑ CSF volume

      • –

        Subset of ventriculomegaly

      • –

        Onset over days (acute), weeks (subacute), or months to years (chronic)

IMAGING

General Features

  • Best diagnostic clue

    • Shunt failure: Dilated ventricles + edema (“blurring”) around ventricles and along catheter, reservoir

  • Location

    • VP shunt common; VA and VPL used rarely unless VP contraindicated

  • Size

    • Ventricular size is relative → ventriculomegaly may indicate shunt failure in 1 patient and be stable finding in another

      • –

        Change in ventricular size in individual patient probably significant

      • –

        Conversely, some patients manifest shunt failure with minimal to no change in ventricular size

    • Distal catheter must be sized long enough to permit somatic growth, prevent retraction out of abdomen or chest

  • Morphology

    • Shunt system components

      • –

        Proximal catheter in ventricles, subarachnoid space, syrinx cavity, or thecal sac

      • –

        Unidirectional valve prevents reflux into ventricles

      • –

        Reservoir used to sample CSF, acutely relieve pressure

      • –

        Distal catheter tunneled through subcutaneous tissues → tip in peritoneal cavity, cardiac atrium, or pleural cavity

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