Discussion:
Total intracranial migration of VP shunt is an extremely rare
complication. The incidence of total migration of VP shunt is reported
to be about 0.1-0.5% (. The migration can take place in either cranial
or caudal directions. Commonly, it is usually the distal or peritoneal
catheter that migrates after disconnecting into many locations such as
the scalp, mouth, thorax, diaphragm, heart, pulmonary artery, chest,
breast, stomach, gall bladder, liver, scrotum, colon, bladder, vagina
and rectum and causing injury to the local organs . However, upward
migration has been reported as well. After a thorough review of
literature, we found twenty-seven cases up to date of total intracranial
VP shunt migration (Table 1).
Etiology of this complication is unknown, but several factors are
thought to be responsible in facilitating proximal shunt migration. It
is believed that the direction of shunt migration is dependent upon the
pressure gradients between cranial and peritoneal cavities. Furthermore,
it is hypothesized that pediatric patients are at an increased risk due
to the shorter distance between the peritoneum and cranium. This short
distance and violent, uncontrolled movements of the head (windlass
effect) could lead to mechanical displacement of the shunt in cranial
direction (. Another possible mechanism of proximal shunt migration may
be due to inadequate fixation of shunt at the distal end or detachment
due to an increased rate of growth in early stages of life. In addition,
thin cerebral mantle, large ventricles and wide fontanelles create an
intracranial pressure close to the atmospheric pressure while abdominal
pressure remains positive in comparison to the atmosphere. This creates
a pressure gradient which can lead to sucking of the shunt towards
cranium . Interestingly, many other case studies report patient-related
factors such as malnutrition (less subcutaneous tissue for anchorage),
anemia, young age, thin cortical layer, and severe hydrocephalus which
could all be related to upward shunt migration . Some authors propose
factors like seizures, and constipation as responsible for possible
migration (. In most VP shunt insertions, a burr hole is made in the
occiput providing a straight path up from the peritoneum . Although this
may be the easiest mode of insertion, it may contribute to cranial shunt
migration as the path is simply too straightforward. Finally, in
resource poor settings like ours “Chhabra” shunt is used as it is very
economical for patients. However, it has cylindrical chamber which can
easily slide into the cranium (. The best approach would be a frontal
burr hole instead of occipital burr hole. Further, optimum creation of
subgaleal space, the firm anchoring of connector sites to the periosteum
while avoiding the large dural opening and large burr holes can help
prevent such complications (2).