Pediatric emergency medicine trisk 1163

is usually obstructed by choroid plexus, but floating debris or hypercellular CSF
can result in the same obstruction; the distal catheter can be obstructed by the
surrounding omentum or can be kinked or coiled. Both proximal and distal
portions can be occluded by the products of infection or by migration of the
catheter tip into the brain parenchyma or intra-abdominal structures. Poor
absorption of excess fluid in the peritoneum due to decreased surface area can
create the appearance of luminal obstruction, particularly in neonates. In addition,
as the child grows, the tension on the shunt system can lead to disconnection of
the distal tubing.
Up to 60% of patients with CSF shunts experience a shunt malfunction in their
lifetime, most commonly within the first 6 months of initial shunt placement.
Parental history is paramount in deciding whether a child is experiencing
symptoms of shunt malfunction. The parent often notices that the child “just isn’t
acting right” or is less active or thinking less clearly than usual. The statement,
“This is exactly how he acted the last time his shunt was obstructed,” is
suggestive of another malfunction, regardless of the presence or absence of the
symptoms listed in the following section.
Common signs and symptoms of mechanical shunt failure include headache,
visual disturbances, vomiting, lethargy, and irritability ( Table 135.2 ). The astute
parent or clinician may note mild ataxia, increased head circumference or bulging
fontanel in an infant, swelling at the reservoir site, poor cognition, or abnormal
behaviors. A classic sign is “sunsetting eyes,” which is really an upgaze paresis
and eyelid retraction associated with Parinaud syndrome from pressure on the
quadrigeminal plate by a dilated suprapineal recess in direct communication with
the third ventricle. Increased tone, hyperreflexia, or Babinski reflex represents
stretching and disruption of the corticospinal fibers originating from the motor
cortex and can suggest shunt malfunction in a patient with a previously normal
examination, although these symptoms are rarely present in a child without a
severe alteration of consciousness. Patients with Cushing triad (hypertension,
bradycardia, and abnormal respiratory pattern) require immediate maneuvers to
decrease ICP and guide them quickly toward operative repair of the shunt.

Seizures are uncommon as the sole manifestation of CSF shunt malfunction.
However, seizures can occur in children who have predisposing brain lesions, and
many patients with CSF shunts have epilepsy. Shunt infection must be considered
in the child with symptoms of shunt malfunction, especially if the child has a
history of recent shunt revision. Ronan et al. reported that more than one-third of
patients with shunt infection presented with symptoms of malfunction.


If the history and physical examination of the ill child with a CSF shunt
suggests a possible shunt malfunction, further evaluation includes urgent
neuroimaging with either noncontrast computed tomographic (CT) scan or MRI,
with comparison to the most recent prior study, if available. Some MRIs may
miss the location of the shunt tip, and will likely reset a programmable shunt, so
one should have access to a programming magnet if MRI is used in a patient with
this type of device. The choice of imaging is based on institutional preference and
techniques used. Ultra low-dose helical CT protocols can be used to lower the
radiation risk to the patient, and scout lateral radiographs that include entire neck
to clavicles can reduce the need for plain radiographs or “shunt series,” which is
most helpful in assessing the integrity of the shunt connection and in identifying
the components of the working system. A formal shunt series radiograph study
should also be considered if there is localized swelling or pain along the shunt
tubing, distal erosions (rare) with shunt tubing present outside the body, or at
request of neurosurgery team to assist with shunt revision. Abdominal ultrasound
can help evaluate for pseudocyst in patients with abdominal symptoms,
particularly in those patients who may have an unreliable abdominal examination
due to sensory deficit or neurologic disease.


TABLE 135.2
CONCERNING FINDINGS IN PATIENTS WITH CEREBROSPINAL

FLUID SHUNT MALFUNCTION
Symptoms
Fever
Headache
Altered mental status
Irritability
Lethargy/difficult arousal
Confusion
Vomiting
Visual disturbances
Seizures (rare to be the only manifestation)
Signs
Papilledema
Bulging fontanel/enlarged head
Engorged head veins
Macewen sign (cracked pot sound during percussion)
Abnormal neurologic examination
Increased deep tendon reflexes or lower-extremity tone
Positive Babinski sign
Cranial nerve palsy—lateral (sixth) or upward (fourth) gaze (sunsetting)
Respiratory compromise
The clinical suspicion of a shunt malfunction based on history and physical
examination may outweigh the data obtained from radiographic studies because
shunt failure may occur without radiographic signs. Pumping the shunt to test for
obstruction is not always reliable. In addition, pumping of the shunt can cause
entrapment of choroid plexus in the proximal shunt tubing and lead to proximal
catheter obstruction where none previously existed. A new technique
(ShuntCheck) that measures a reduction in distal neck temperature over the shunt
after placing an ice bag proximally on the neck shows promise for confirming
shunt flow but has not yet been published in the peer-reviewed literature.

FIGURE 135.4 Tapping the cerebrospinal fluid shunt.

If subsequent evaluation is still necessary to diagnose malfunction, a
neurosurgeon should be consulted. It may be necessary to “tap” the shunt ( Fig.
135.4 ). The patient’s hair is either shaved or trimmed. The scalp is cleansed first
with alcohol and then with three applications of Betadine that are allowed to dry