Hydrocephalus Ventriculo-peritoneal shunt

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HydrocephalusVentriculo-peritoneal shunt

• Diana Tanase

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Ventricular system
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HydrocephalusEtiology

• subnormal CSF reabsorption
• rarely CSF overproduction
• which result in accumulation of CSF in the
  ventricular system

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FUNCTIONAL CLASSIFICATION

• Two main functional subdivisions of hydrocephalus
  (HCP)
• obstructive (AKA non-communicating) block
  proximal to the arachnoid granulations(AG).
• 2. communicating (AKA non-obstructive) CSF
  circulation blocked at level of AG

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SPECIAL FORMS OF HYDROCEPHALUS AND
"PSEUDOHYDROCEPHALUS"

• 1. conditions that are not actually hydrocephalus
  "pseudohydrocephalus"
• A. hydrocephalus ex vacuo cerebral atrophy
• B. otitic hydrocephalus
• C. external hydrocephalus
• D. Hydranencephaly
• 2. normal pressure hydrocephalus (NPH)
• 3. entrapped fourth ventricle
• 4. arrested hydrocephalus

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Normal pressure hydrocephalus-adult form of
hydrocephalus-

• As originally described, the hydrocephalus of NPH
  was considered to be idiopathic.
• "secondary NPH causes
• 1. post-SAH
• 2. post-traumatic
• 3. post-meningitis
• 4. following posterior fossa surgery
• 5. tumors
• 6. also seen in some patients with Alzheimer's
  disease (AD)
• 7. deficiency of the arachnoid granulations
• 8. aqueductal stenosis

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Clinical triadHakim triad

• 1. gait disturbance
• 2. dementia primarily memory impairment with
  bradyphrenia (slowness of thought) and
  bradykinesia
• 3. urinary incontinence

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Other clinical features

• Age usuallygt 60 yrs.
• Slight male preponderance.
• Differential diagnosis
• Alzheimer's disease
• Parkinson's disease

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Hydrocephalus Classification

• Congenital
• Acquired

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Congenital, usually paediatric

• A. Chiari Type 2 malformation and/or
  myelomeningocele (MM)
• B. Chiari Type 1 malformation
• C. primary aqueductal stenosis of Sylvius
  aqueduct
• D. secondary aqueductal gliosis
• E. Dandy Walker malformation atresia of foramina
  of Luschka Magendie
• F. X-linked inherited disorder rare

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Acquired

• A. infectious
• 1. post-meningitis
• 2. cysticercosis
• B. post-hemorrhagic
• 1. post-SAH
• 2. post-intraventricular hemorrhage (IVH)
• C. secondary to masses
• 1. non neoplastic e.g. vascular malformation
• 2. neoplastic e.g. Medulloblastoma, pituitary
  tumor
• D. post-op following p-fossa tumor removal.
• E. Neurosarcoidosis
• F. "constitutional ventriculomegaly"
  asymptomatic. No treatment required.
• G. associated with spinal tumors

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DIFFERENTIAL DIAGNOSIS OF HYDROCEPHALUS

• Conditions that may mimic HCP but are not due to
  inadequate CSF absorption include
• 1. atrophy sometimes referred to as
  "hydrocephalus ex vacuo"
• 2. hydranencephaly
• 3. developmental anomalies where the ventricles
  appear enlarged
• A. agenesis of the corpus callosum
• B. septa-optic dysplasia

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SIGNS AND SYMPTOMS OF ACTIVE HCP

• In young children
• 1. cranium enlargement
• 2. irritability, poor head control, NN
• 3. fontanelle full and bulging
• 4. enlargement and engorgement of scalp veins
• 5. Macewents sign cracked pot sound on
  percussing over dilated ventricles
• 6. 6th nerve (abducens) palsy
• 7. "setting sun sign" (upward gaze palsy)
• 8. hyperactive reflexes
• 9. irregular respirations with apneic spells
• 10. splaying of cranial sutures
• In older children/adults with rigid cranial vault
• Symptoms of increased ICP, including
• - papilledema,
• - HI A,
• - NN,
• - gait changes,

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CHRONIC HCP

• Features indicative of chronic hydrocephalus (as
  opposed to acute hydrocephalus)
• 1. beaten copper cranium on plain skull x-ray.
• 2. 3rd ventricle herniating into sella (seen on
  CT or MRI)
• 3. erosion of sella turcica
• 4. the temporal horns may be less prominent on CT
  than in acute HCP
• 5. Macrocrania
• 6. atrophy of corpus callosum
• 7. in infants
• A. sutural diastasis
• B. delayed closure of fontanelles
• C. failure to thrive or developmental delay

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CT/MRI CRITERIA OF HYDROCEPHALUS

• Hydrocephalus HCP is suggested when either
• both TH 2 mm in width
• OR
• B. both TH 2 mm
• ratio FH/ID gt 0.5
• TH temporal horns
• FH the largest width of the frontal horns
• ID the internal diameter

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Other features suggestive of hydrocephalus

1. ballooning of frontal horns of lateral ventricles
   ("Mickey Mouse" ventricles) and/or 3rd ventricle

2. periventricular low density on CT
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• 3. used alone, the ratio FH/ID
• lt40 normal
• 40-50 borderline
• gt50 suggests hydrocephalus
• 4. Evans ratio (or index) ratio of FH to BPD
  measured in the same CT slice
• gt 0.3 suggests hydrocephalus
• 5. sagittal MRI may show thinning and/or upward
  bowing of the corpus callosum

BPD maximal biparietal diameter
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Treatment of hydrocephalus

• MEDICAL
• Acetazolamide may be helpful for temporizing.
• Diuretic therapy may be tried in premature
  infants with bloody CSF.
• This should only be considered as an adjunct to
  definitive treatment or as a temporizing measure.
• acetazolamide (a carbonic anhydrase inhibitor)
  25 mg/kg/day
• simultaneously start furosemide 1 mg/kg/day
• to counteract acidosis
• tricitrate 4 ml/kg/day
• measure serial electrolytes, and adjust dosage
  to maintain serum HCO3 gt 18mEq/L
• watch for electrolyte imbalance and
  acetazolamide side effects lethargy, tachypnea,
  diarrhea, paresthesias (e.g. tingling in the
  fingertips)
• perform weekly U/S or CT scan and insert
  ventricular shunt if progressive ventriculomegaly
  occurs. Otherwise, maintain therapy for a 6 month
  trial, then taper dosage over 2-4 weeks. Resume
  3-4 mos of treatment if progressive HCP occurs

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SPINAL TAPS

• HCP after intraventricular hemorrhage may be only
  transient Serial taps (ventricular or LP) may
  temporize until resorption resumes but LPs can
  only be performed for communicating HCP.
• If reabsorption does not resume when the protein
  content of the CSF islt 100 mg/dl, then it is
  unlikely that spontaneous resorption will occur
  (i.e. a shunt will usually be necessary).

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SURGICAL

• Goals of therapy
• Normal sized ventricles is not the goal of
  therapy. Goals are optimum neurologic function
  and a good cosmetic result.
• Options include
• 1. choroid plexectomy for communicating
  hydrocephalus
• May reduce the rate but does not totally halt
  CSF production (only a portion of CSF is secreted
  by the choroid plexus, other sources include the
  ependymal lining of the ventricles and the dural
  sleeves of spinal nerve roots).
• 2. eliminating the obstruction e.g. opening a
  stenosed sylvian aqueduct.
• 3. third ventriculostomy
• 4. shunting

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Third ventriculostomy

• Indications
• used in patients with obstructive HCP
• an option in managing shunt infection
• an option for patients who developed subdural
  hematomas after shunting
• for slit ventricle syndrome.
• Contraindications Communicating hydrocephalus
• Complications
• 1. hypothalamic injury
• 2. transient 3rd and 6th nerve palsies
• 3. uncontrollable bleeding
• 4. cardiac arrest
• 5. traumatic basilar artecy aneurysm
• Success rate
• 56 Highest maintained patency rate is with
  previously untreated acquired AqS.
• There is a low success rate (only 20 of TVs
  will remain patent) if there is pre-existing
  pathology including
• 1. tumor
• 2. previous shunt

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TYPES OF SHUNTS

• SHUNT TYPE BY CATEGORY
• 1. ventriculoperitoneal (VP) shunt
• A. most commonly used shunt
• B. lateral ventricle is the usual proximal
  location
• 2. ventriculo-atrial (VA) shunt ("vascular
  shunt")
• A. ventricles -gt jugular vein -gt superior vena
  cava
• B. treatment of choice when abdominal
  abnormalities are present
• 3. Torkildsen shunt
• A. shunts ventricle to cisternal space
• B. rarely used
• C. effective only in acquired obstructive HCP

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TYPES OF SHUNTS

• 4. miscellaneous used historically or in
  patients who have had significant problems with
  traditional shunt locations
• A. pleural space (ventriculopleural shunt) not
  a first choice, but a viable alternative if the
  peritoneum is not available.
• B. gall bladder
• C. ureter or bladder causes electrolyte
  imbalances
• 5. lumboperitoneal (LP) shunt
• - only for communicating HCP
• 6. cyst or subdural shunt from arachnoid cyst or
  subdural hygroma cavity, usually to peritoneum

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Shunts

• Ventricular catheterization
• Most common insertion sites
• 1. occipital-parietal region commonly used for
  CSF shunt
• A. entry site a number of means have been
  described, including
• 1. Frazier burr hole placed prophylactically
  before p-fossa crani for emergency
  ventriculostomy in event of post-op swelling.
• Location 3-4 cm from midline, 6-7 cm above
  inion
• 2. parietal boss
• 3. follow point from mid-pupillary line
  parallel to sagittal suture until it intersects
  line extending posteriorly from the top of the
  pinna
• 4. 3 cm above and 3 cm posterior to top of
  pinna
• B. trajectory insert the catheter parallel to
  skull base
• - aim for middle of forehead
• C. insertion length ideally, the tip should be
  just anterior to the foramen of Monro in the
  frontal horn.

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3. Dandy's point 2 cm from midline, 3 cm above
inion (may be more prone to damage visual
pathways than above)

• 2. Keen's point (posterior parietal) (placement
  in trigone) 2.5-3 cm posterior and 2.5-3 cm
  superior to pinna

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4. Kocher's point (coronal) places catheter in
frontal horn. The right side is usually used.
Commonly employed for ICP monitors

• A. entry site 2-3 cm from midline which is
  approximately the mid-pupillary line with forward
  gaze, 1 cm anterior to coronal suture (to avoid
  motor strip)
• B. trajectory direct catheter perpendicular to
  surface of brain, aiming in coronal plane towards
  medial canthus of ipsilateral eye and in AP plane
  towards EAM
• C. insertion length advance catheter with stylet
  until CSF is obtained
• (should be lt 5-7 cm depth this may be 3-4 cm
  with markedly dilated ventricles).
• Advance catheter without stylet 1 cm deeper.
• CAUTION if CSF is not obtained until very long
  insertion length (e.g. 8 cm) the tip is probably
  in a cistern (e.g. prepontine cistern) which is
  undesirable

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Ventriculostomy/ICP monitor

• AKA intraventricular catheter (IVC) or external
  ventricular drainage (EVD).
• INSERTION TECHNIQUE
• The right (non-dominant) side is preferred.
• Five minute Betadine prep.
• Site approximately Kocher's point.
• To avoid motor strip, enter 1-2 cm anterior to
  coronal suture
• estimated position of coronal suture follow
  line up midway between lateral canthus and EAM,
  and to avoid the sagittal sinus, 2-3 cm lateral
  to midline.
• Incision oriented in sagittal plane
• elevate periosteum
• place self-retaining retractor
• make twist drill hole.
• Bone-wax edges to stop bone bleeding
• cauterize dura with bipolar coagulator
• incise dura in cruciate fashion with 11 scalpel
  blade
• cauterize incised dural edges and then
  pia/arachnoid with bipolar.

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• For ventriculostomy
• insert catheter perpendicular to brain surface to
  a depth of 5-7 cm.
• With any ventricular enlargement, CSF should flow
  at least by 3-4 cm depth.
• If no CSF is encountered here and the catheter is
  passed further until CSF is obtained, it is
  unlikely to be due to catheterization of frontal
  horn of lateral ventricle.
• If unsuccessful after a maximum of three
  attempted passes, then place a subarachnoid bolt
  or intraparenchymal monitor.

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• REMOVAL
• Patients receiving anticoagulants need to have
  normal coagulation and platelet function before
  discontinuing the catheter to reduce the risk of
  intracranial hemorrhage.
• For heparin and LMW heparin, stop the drug 24
  hours prior to discontinuing the drain.
• SUMP DRAINAGE
• The tip of a 25 gauge butterfly may be bent at a
  90 angle, and inserted into a subcutaneous
  reservoir for prolonged ventricular drainage.
• The use of a one-way valve, continuous
  antibiotics (ampicillin and cloxacillin) and
  meticulous technique was credited for the lack of
  infection.

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Ventricular shunts

• 1. position supine with shoulder roll
• 2. Implants
• 3. equipment
• A. C-arm for ventriculo-atrial shunts
• B. endoscopic display (e.g. If NeuroPen is used)
• C. image guided navigation system (infrequently
  used)
• 4. consent (in lay terms for the patient- not
  all-inclusive)
• A. procedure surgery to insert a permanent
  drainage tube from the brain to the abdomen,
  outside of the lungs, vein near the heart (as
  appropriate) to drain excess cerebrospinal fluid
• B. alternatives nonsurgical management (rarely
  effective for hydrocephalus), third
  ventriculostomy (for certain cases)
• C. complications infection, suboptimal position
  which might require re-operation, failure to
  relieve hydrocephalus/symptoms, subdural
  hematoma, bleeding in the brain, shunts are
  mechanical devices and will eventually fail
  (break, block up, move ... ) and need
  repair/replacement (sometimes sooner rather than
  later). Abdominal shunts risk of bowel injury
  (which could require further surgery)

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Ventricular catheter

• Occipital burr hole is used in most cases for
  insertion site of ventricular catheter.
• Some prefer a frontal burr hole (Kocher's point)
  citing a lower incidence of failure from choroid
  plexus occlusion.
• An inverted "J" shaped incision is used to keep
  hardware from lying directly under the skin
  incision (minimizes risk of skin breakdown and
  also creates additional barrier to infection of
  subjacent hardware).
• CSF should be sent for culture at the time of
  insertion since it has been estimated that in 3
  of patients the CSF is already infected.
• 4 mg of preservative-free gentamicin may be
  instilled into the ventricular catheter by the
  technique of barbotage.
• If you think the catheter is in the ventricle,
  but you don't get CSF flow, it may be due to low
  pressure, you can compress the jugular veins or
  lower the head of the bed to try and induce CSF
  flow.
• Connectors
• If a connector must be used near the clavicle,
  placing it below the clavicle increases the risk
  of disconnection vs. placing the connector above
  the clavicle.

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DISTAL CATHETER PLACEMENT

• The general order of preference for distal
  catheter placement
• peritoneal cavity
• pleural space
• right atrium or superior vena cava
• less frequently used distal shunt sites
• A. gall bladder
• B. internal jugular vein
• C. superior sagittal sinus

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VENTRICULOPERITONEAL SHUNT

• Peritoneal catheter
• For small children, use at least 30 cm length of
  intraperitoneal tubing to allow for continued
  growth (120 cm total length of peritoneal tubing
  recommended).
• A silver clip is placed at the point where the
  catheter enters the peritoneum so that the amount
  of residual intraperitoneal catheter can be
  determined on later films.
• Distal slits on the peritoneal catheter may
  increase the risk of distal obstruction, and some
  authors recommend that they be trimmed off.

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Open technique A vertical incision lateral and
superior to the umbilicus is one of several
choices.

• Layers
• 1. subcutaneous fat
• 2. anterior rectus sheath
• 3. abdominis rectus muscle fibers should be
  split longitudinally
• 4. posterior rectus sheath
• 5. preperitoneal fat
• 6. peritoneum

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• Trocar technique
• 1. place a Foley catheter to decompress the
  bladder
• 2. 1 cm skin incision above and lateral to the
  umbilicus
• 3. pull abdominal skin anteriorly (away from
  patient)
• 4. insert trocar aiming toward the ipsilateral
  iliac crest
• 5. feel 2 "pops" of penetration 1 anterior
  rectus sheath, 2 posterior rectus
  sheath/peritoneum
• 6. peritoneal catheter should feed easily through
  trocar

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VP SHUNT, POST-OP ORDERS (ADULT)

• flat in bed
• if peritoneal end is new or revised, do not feed
  until bowel sounds resume (at least 24 hrs)
• 3. shunt series (AP lateral skull, and chest/
  abdominal x-ray) as baseline for future
  comparison

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Disadvantages/complications of various shunts

• Those that may occur with any shunt
• A. obstruction the most common cause of shunt
  malfunction
• proximal ventricular catheter (the most common
  site)
• valve mechanism
• distal
• B. disconnection at a junction, or break at any
  point
• C. infection
• D. hardware erosion through skin, usually only in
  debilitated patients
• E. seizures (ventricular shunts only)
• Seizure risk is questionably higher with frontal
  catheters than with parieto-occipital.
• F. act as a conduit for extraneural metastases of
  certain tumors (e.g. medulloblastoma).
• Low risk.
• G. silicone allergy rare.
• May require fabrication of a custom
  silicone-free device (e.g. polyurethane)

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Disadvantages/complications of VP shunts

• inguinal hernia
• need to lengthen catheter with growth
• C. obstruction of peritoneal catheter
• D. peritonitis from shunt infection
• E. hydrocele
• F. CSF ascites

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• G. tip migration
• into scrotum
• perforation of a viscus stomach, bladder
• through the diaphragm
• H. intestinal obstruction (as opposed to
  perforation) rare
• I. volvulus
• J. intestinal strangulation
• K. overshunting more likely than with VA shunt.
  Some recommend LP shunt for communicating
  hydrocephalus.

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MISCELLANEOUS SHUNT HARDWARE

• 1. tumor filter used to prevent peritoneal or
  vascular seeding in tumors that may metastasize
  through CSF (e.g. medulloblastoma, PNETs,
  ependymoma) may eventually become occluded by
  tumor cells and need replacement
• 2. antisiphon device prevents siphoning effect
  when patient is erect
• 3. "horizontal-vertical valve" (H-V valve) used
  with LP shunts to increase the valve resistance
  when the patient is vertical to prevent
  overshunting
• 4. variable pressure valves that may be
  externally programmed
• 5. on-off device used to open or occlude shunt
  system by external manipulation of shunt

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Programmable shunt valves

• Components
• Inlet occluder
• Reservoir
• Outlet occluder
• One-way valve
• Pressure settings

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Shunt problems

• Problems associated with shunt insertion
• Problems in patients with established CSF shunt

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Problems associated with shunt insertion

• intraparenchymal or intraventricular hemorrhage
• Seizures
• malposition
• A. of ventricular catheter
• B. of distal catheter
• 4. infection

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Problems in patients with established CSF shunt

• Shunt "problems" usually involve one or more of
  the following
• Undershunting
• infection
• 3. overshunting slit ventricle syndrome,
  subdural hematomas
• 4. seizures
• 5. problems related to the distal catheter
• A. peritoneal
• B. atrial
• 6. skin breakdown over hardware infection or
  silicone allergy
• 7. hemorrhage at time of insertion uncommon in
  pediatrics

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Overshunting-slit ventricles-

• -subdural hematomas-

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TAPPING A SHUNTaka aspirating a shunt

• Indications to tap a shunt or ventricular access
  device include
• 1. to obtain CSF specimen
• A. to evaluate for shunt infection
• B. for cytology
• C. to remove blood
• 2. to evaluate shunt function
• A. measuring pressures
• B. contrast studies
• 3. as a temporizing measure to allow function of
  a distally occluded shunt
• 4. to inject medication
• A. antibiotics for shunt infection or
  ventriculitis
• B. chemotherapeutic (antineoplastic) agents
• 5. for catheters placed within tumor cyst (not a
  true shunt)
• A. periodic withdrawal of accumulated fluid
• B. for injection of radioactive liquid (usually
  phosphorous) for ablation

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