From the Guidelines
Shunt evaluation should be pursued immediately when a patient with a cerebrospinal fluid (CSF) shunt presents with symptoms suggesting possible shunt malfunction or infection, such as new or changed mental status alteration, nausea and vomiting, or gait abnormality, as indicated by the 2016 IDSA clinical practice guideline 1.
Key Symptoms for Shunt Evaluation
- New or changed mental status alteration
- Nausea and vomiting
- Gait abnormality
- Headache
- Seizures
- Visual changes
- Decreased level of consciousness
- For infants and young children: irritability, lethargy, bulging fontanelle, increased head circumference, or developmental regression
- Fever, redness, or tenderness along the shunt tract may indicate infection
Evaluation Approach
The evaluation typically involves:
- Neuroimaging (CT or MRI) to assess ventricular size compared to baseline, with consideration of rapid MRI to reduce lifetime radiation exposure when available 1
- Shunt series X-rays to check for disconnection or breakage
- Potentially a shunt tap to measure pressure and obtain CSF for analysis, taking into account the possibility of introducing a shunt infection or causing a malfunction with this intervention 1
- Comparison with the patient’s prior imaging to detect subtle changes in ventricular size, as interpreting neuroimaging in patients with concern for shunt malfunction is best performed when compared with the patient’s prior imaging 1
Importance of Prompt Evaluation
Prompt evaluation is crucial as untreated shunt malfunction can lead to increased intracranial pressure and potentially life-threatening complications. Even if symptoms are mild or vague, it's better to evaluate the shunt when there's clinical suspicion, as early intervention improves outcomes.
From the Research
Indications for CSF Shunt Evaluation
- Shunt malfunction may be caused by shunt infection, which may not be clinically apparent by standard diagnostic criteria 2
- Unusual presentations of shunt malfunction may occur, such as pleuritic chest pain, cough, and fever 3
- Mental status change and headache are symptoms most concordant with shunt malfunction, but no symptom has a predictive value much better than 50% 4
- A high index of suspicion for shunt infection or malfunction must be maintained when evaluating the patient with a cerebrospinal fluid shunt 5
Diagnostic Approaches
- CSF culture alone does not rule out infection in cases of shunt malfunction 2
- Shunt tap may not be obligatory as a routine test of the device's patency, and other diagnostic approaches such as CT scans, lumbar puncture, and x-ray "shunt series" may be used 4
- A separate reservoir placed at the site of the shunt can be useful in evaluating shunt malfunction and detecting shunt infection 6