Keywords
cerebrospinal fluid leak - hydrocephalus - ventriculoperitoneal shunt
Introduction
Ventriculoperitoneal (VP) shunt placement is a common neurosurgical procedure used
to treat hydrocephalus by removing excess cerebrospinal fluid (CSF) from the ventricles
to facilitate resorption by the peritoneum. In the United States, data from the Healthcare
Cost and Utilization Project Kids' Inpatient Database (KID) indicates that between
2,500 and 3,300 VP shunts are placed in the pediatric population aged 0 to 18 years
every year.[1]
[2] However, despite their efficacy in treating hydrocephalus, 30 to 40% of pediatric
shunts fail within the first year, with most requiring a revision in their lifetime.[3] Overall, the most common causes of shunt failure include mechanical obstruction
due to blockage, catheter breakage or migration (including extraperitoneal perforations),
followed by infections.[4]
[5] In the pediatric population specifically, ventricular catheter obstruction with
tissue, commonly either from glial tissue or the choroid plexus, has been reported
to cause over 50% of shunt failures.[6]
Case Presentation
We present a 16-month-old fraternal twin male born at 35 weeks and 5 days gestational
age via cesarean section. He was born with a myelomeningocele and associated Chiari
II malformation and underwent surgical repair of the former immediately after birth.
His infancy was complicated by hydrocephalus, which was treated by VP shunt placement
at age 6 days. Fifteen months after the shunt was placed, he presented to the emergency
department with a 2-day history of clear fluid draining from the scrotal sac with
acute onset of emesis and progressive lethargy. One week prior to this admission,
the patient had undergone a right orchiopexy for an undescended testes and indirect
inguinal hernia repair, made challenging by testicular adhesions to the abdominal
wall and scarring in the inguinal canal secondary to irritation and inflammation from
the VP shunt. In the emergency department, he was found to have leukocytosis and anion
gap acidosis. On physical examination, vital signs were stable and clear fluid was
dripping from the right scrotal incision.
CSF from the shunt reservoir was sent for analysis. Given the high concern for CSF
leak and VP shunt infection, he was started on empiric antibiotics for meningitis
by the emergency department. Computed tomography (CT) demonstrated an intact right
VP shunt with the catheter tip in the right lateral abdomen without obstruction or
mechanical failure. Ultrasound of the abdomen and scrotum showed fluid collection
within the right scrotal sac. Computed tomography (CT) of the abdomen and pelvis demonstrated
the distal VP shunt catheter within the right inguinal canal, draining CSF into the
scrotum via a patent processus vaginalis ([Fig. 1]).
Fig. 1 Coronally oriented CT demonstrating malpositioned tip of the distal shunt within
the right inguinal canal with a patent processus vaginalis and CSF within the right
scrotal sac (white asterisk).
Given these radiographic findings, decision was made to externalize the shunt and
repair the scrotal dehiscence. The procedures were performed without issue and the
patient was monitored postoperatively in the pediatric intensive care unit. Drain
output was continuously monitored and remained stable. Eleven days later, it was determined
that the scrotal dehiscence and urological interventions to close the patent processus
vaginalis had healed enough to re-internalize the shunt. CSF cultures (including the
original samples from the VP shunt reservoir) remained negative. The distal catheter
was re-internalized into the patient's abdomen without complication. The patient was
discharged home on postoperative day 3. The patient has been doing well without return
of symptoms or other postoperative concerns at 12-months follow-up.
Discussion
Despite their efficacy, VP shunt failure and revision rates remain high. Mechanical
failures such as obstruction, disconnections, and migrations are the most common cause
of revisions, followed by infections.[4]
[5] In pediatric populations, cranial obstructions, usually of the ventricular catheter,
and hardware misplacement comprise most complications.[6]
[7] While less common, migrations have the potential to cause significant distress to
patients due to improper drainage resulting in a recurrence of hydrocephalus, fluid
accumulations in areas that cannot sufficiently resorb CSF, bowel perforations and
obstructions, or, in rare cases, extraperitoneal perforations.
While uncommon, extraperitoneal migrations have been reported in the literature occurring
at various locations, most commonly the bowel and genitourinary tract.[8] Distal portions of VP shunts have been found in the vagina, pericardium, lung, bladder,
and scrotum.[9]
[10]
[11]
[12]
[13] Shunt migrations have been found to occur mainly within the first year of placement,
are more common in children than adults, and when exposure to the external environment
occurs, are associated with a greater than 50% chance of infection.[8]
Scrotal migrations usually occur in infants with a patent processus vaginalis although
a few adult cases have been reported.[14]
[15] Scrotal migration is theorized to occur during infancy and the first few years of
life as a result of the increased intraperitoneal pressure created by the VP shunt
and the resultant maintained patency of the processus vaginalis, usually present on
the right side.[16]
[17] Our patient's case was complicated by recent urological surgery on that side. In
most cases, migration results in hydroceles that are treated via surgical repositioning
or removal of the shunt with subsequent obliteration of the processus vaginalis.[14]
[15]
[16]
[18]
[19] Rarely these migrations may cause scrotal perforations and greatly increase the
risk of infection.[20]
[21]
This case represents a unique presentation of CSF leak secondary to scrotal migration,
which nearly went undiagnosed due to its rarity. Repair of the underlying embryological
condition via scrotal or inguinal canal surgery may serve as an entryway for VP shunt
infection. Thus, surgeons and other clinicians should take extra caution to avoid
this risk.
