Keywords
CSF flow problem - hydrocephalus - neurology - neurosciences - neurosurgery - pediatrics
Introduction
Pediatric hydrocephalus manifests in approximately 1 in every 1,000 live births and
is speculated to potentially exhibit a higher prevalence in developing countries.[1] Ventriculoperitoneal (VP) shunt is still a mainstay of treatment in many centers,
for infants with aqueductal stenosis which is the most common cause of congenital
obstructive hydrocephalus.[2] Shunt migration remains a common complication.[3] However, distal tip migration into the thoracic cavity due to negative intrathoracic
pressure is a rare occurrence.[4]
Case Presentation
We report a 1-year-old infant presenting with drowsy sensorium, increasing head circumference,
and bulging anterior fontanelle. The above clinical signs were suggestive of raised
intracranial pressure probably due to hydrocephalus which is a common problem in this
age group. Magnetic resonance imaging of the brain ([Fig. 1]) revealed gross obstructive hydrocephalus with periventricular seepage due to aqueductal
stenosis. Additionally, a large expansile diverticulum of the suprapineal recess extending
infratentorially over the dorsal midbrain and cerebellum inferiorly with a compressed
4th ventricle was noted (arrow mark). The child underwent an emergency right-side
VP shunt (medium pressure). The cranial end was inserted via a keen point burr hole
into the lateral ventricle, with a trajectory toward the frontal horn. On tapping
the ventricle, the catheter was connected to a pressure transducer monitor which measured
the cerebrospinal fluid (CSF) pressure to be at 9 cm H2O, thus justifying the need
for a medium pressure shunt. A blunt-tip stainless steel shunt tunneler was used to
create a subcutaneous passage from the cranial site into a transverse infraumbilical
incision in the right iliac fossa. There were no intrathoracic pressure changes during
the procedure. Visual confirmation of the bowel was done after opening the peritoneum
by two operating surgeons prior to inserting the distal catheter. The child's sensorium
improved, was feeding well, and was discharged on postoperative day 3. The child presented
3 months later with acute dyspnea and diminished breath sounds on the right hemithorax.
Neurologically, the child was active and anterior fontanelle was lax. A chest roentgenogram
([Fig. 2]) and computed tomogram (CT) ([Fig. 3]) of the thorax revealed complete shunt migration into the pleural space with significant
pleural effusion on the right side. The distal shunt system on CT appeared to enter
the pleural space below the 8th rib, probably indicating that there was subcostal
tunneling of the shunt below the 8th rib space during the first surgery which was
inconspicuous and subsequently over a span of 3 months due to sucking effect of negative
intrathoracic pressure the shunt gradually migrated into the pleural cavity which
led to the effusion. An emergency VP shunt revision was performed. The distal end
below the chamber was retunneled subcutaneously into a new incision in the left paraumbilical
region. Postoperative chest and abdomen roentgenograms showed resolving effusion and
accurate shunt placement ([Fig. 4]). The child required elective ventilation to tide over the underlying collapse of
the lung and an intercostal tube drainage for the CSF hydrothorax to aid in weaning.
The child was discharged on the 5th postoperative day.
Fig. 1 T2 fluid-attenuated inversion recovery (FLAIR) mid-sagittal section showing significant
hydrocephalus, periventricular seepage, and suprapineal recess diverticular extending
below the tentorium causing significant compression over the cerebellum and brainstem.
Anterior diverticulum from the lamina terminalis and infundibular recess extending
to the suprasellar recess. Compressed 4th ventricle (arrow) and aqueductal stenosis.
Fig. 2 Chest roentgenogram showing shunt migration into the pleural space and pleural effusion.
Fig. 3 Computed tomogram (CT) thorax depicting shunt migration and cerebrospinal fluid (CSF)
hydrothorax.
Fig. 4 Postoperative chest and abdomen roentgenogram after revision of the shunt showing
resolving effusion and appropriate shunt repositioning.
Discussion
CSF hydrothorax after VP shunt surgery can be associated, either with shunt system
migration or without shunt system migration.[5]
[6]
[7] Intrapleural migration of VP shunts has been contemplated to be due to trauma during
surgery, migration across foramen of Bochdalek or Morgagni, and negative intrathoracic
pressure.[8] Thoracic migration of VP shunt can lead to effusion, bronchial perforation, pneumothorax,
and pneumonia.[9] Taub and Lavyne have classified thoracic complications of VP shunt as thoracic trauma
during shunt tunneling, supradiaphragmatic migration of shunt or transdiaphragmatic
migration of shunt, and pleural effusion complicated by CSF ascites.[4] Transdiaphragmatic migration is commonly seen in pediatric population and supradiaphragmatic
migration can be seen in any age group.[10] We believe our case to be a type of supradiaphragmatic migration of the shunt, which
has occurred slowly over a span of time due to the sucking effect from negative intrathoracic
pressure. Pleural effusion as a sequela to intrathoracic migration of VP shunt is
due to CSF production-absorption mismatch.[11] What adds to the problem, is the smaller surface area of pleural cavity especially
in pediatric patients. Similar cases of shunt migration with delayed presentation,
even after many years of surgery, have been reported.[7] Before shunt revision it is prudent to rule out meningitis. If infection is present,
a temporary shunt exteriorization may be required until the distal end can be revised.
To prevent inadvertent subcostal tunneling of the shunt, it would be wise to continuously
palpate the tip of the tunneler instrument during the procedure. The overarching aim
of this clinical case illustration is to edify neurosurgeons, pediatricians, and intensivists
to remain wary of such a complication.
