Diagnostics: The Shunt Series
/Introduction
Hydrocephalus is an accumulation of cerebrospinal fluid (CSF) in the cerebral ventricular system secondary to a mismatch between CSF production and resorption. Excessive production of CSF is rare and occurs with choroid plexus papillomas or other tumors. Impaired drainage or resorption of CSF is a far more common cause of hydrocephalus and can occur due to congenital malformations, tumors, trauma, or infection. Rapid development of hydrocephalus in the acute setting presents with signs and symptoms of increased intracranial pressure and represents a surgical emergency because of the risk of herniation syndromes.
Treatment
If a patient is herniating in front of your eyes – hypertensive, bradycardic, altered, and not protecting their airway – secure the ABCs, provide hypertonic fluids (3% normal saline, mannitol), hyperventilate the patient, elevate the head of the bed and call neurosurgery. Definitive management in these, and less acute cases, is often the placement of a ventriculoperitoneal (VP) shunt.
More on this below as we work through a few cases….
Case 1
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A 1-month-old (ex-34 week premature) infant comes to your emergency department for fussiness. He appears well and is triaged to an ESI 4. After waiting for several hours, the family arrives in an examination room and the child appears stuporous. He has a weak cry and you notice bulging fontanelles. After a several week NICU stay for prematurity, the infant has been generally healthy and this is his first trip back to the hospital since discharge. The symptoms started yesterday evening and have been getting worse. A broad infectious and metabolic workup is negative and you decide to obtain cross-sectional head imaging as part of your altered mental status workup. As you scroll through the images, you notice the lateral ventricles appear significantly enlarged.
As you await the formal read, you see an 80-year-old woman with urinary incontinence and confusion. She was brought in from her nursing home and is reported to “always act like this when she has a UTI.” Similarly, your infectious workup is negative and you note that all prior urine cultures failed to grow bacteria when she was treated for UTIs 4 times over the last 6 months. Collateral information from the family indicates that she has been progressively more forgetful, disinhibited, and combative. She is now near totally incontinent and wears a diaper 24 hours a day. You decide to obtain cross-sectional head imaging as part of your altered mental status workup. As you scroll the images, you again notice the lateral ventricles appear significantly enlarged…
What is going on? Who do we need to call?
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Hydrocephalus (congenital vs. idiopathic). Consult neurosurgery!
In the first case, congenital hydrocephalus accounts for approximately 20% of all cases. Prematurity is a risk factor and the exact pathophysiology is poorly understood. Young infants will present with failure to thrive, poor weight gain, and increasingly worsening altered mental status as ICP continues to increase beyond critical values.
In the second case, adults (especially the elderly) are at risk for hydrocephalus that develops insidiously. Because the compensatory mechanisms that regulate ICP are able to calibrate for slowly enlarging ventricles, these patients will often have normal ICP and are therefore termed as having normal pressure hydrocephalus. The presentation is highly variable, but the classic triad of “wet, wild, and wobbly” (urinary incontinence, altered mental status, and gait instability) is rare. Diagnosis is made via CT scan and/or lumbar puncture.
A treatment option for both of these cases is placement of a VP shunt. The idea is over half a century old. Modern VP shunts have a programmable ball-ring valve that allows flow of CSF out of the ventricular system when intraventricular pressure exceeds a preset value. The drainage catheter is tunneled under the skin and terminates in the peritoneal cavity.
Case courtesy of Paul Simkin, Radiopaedia.org, rID: 30453
Case 2
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A 19-year-old male is brought into your emergency department via EMS for witnessed seizure-like activity. The seizure abated with rectal diazepam given by the squad. The patient arrives hemodynamically stable and post-ictal, unable to answer any questions. On exam, you palpate a tube-like structure in the patient’s neck. His abdomen is soft. He is responsive to pain, but is not spontaneously moving his extremities. You notice a med-alert bracelet with the patient’s name and the word “SEIZURES.” You read about the patient’s history of VP shunt placement for aqueductal stenosis as a child and decide to order some imaging…
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Obtain shunt imaging (“shunt series,” CTH non-con)
Shunt series shows no migration of the shunt catheters or fractures of the tubing. CTH demonstrates acute hydrocephalus despite the presence of a VP shunt.
Given the break-through seizures, hydrocephalus on CT, and benign abdomen, you are concerned for a proximal shunt occlusion. This occurs when brain parenchyma, clotted blood, inflammatory cells or cellular debris occludes the drainage catheter from the ventricular system. Shunt failures are quite common with the average patient requiring 2-3 shunt revisions over their first 20 years with the shunt. Amongst shunt mechanical failures, proximal occlusion is the most common cause.
Management of these patients in the emergency department is largely supportive. Shunt malfunction may cause seizures, nausea/vomiting, altered mental status, and headache which should all be treated symptomatically. Unfortunately, maneuvers to relieve a proximal occlusion in the emergency department are limited. Lumbar puncture is an option with limited data for success. Ultimately, definitive management is in the operating room with revision or replacement of the VP shunt.
Case 3
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A 6-year-old boy is brought to the emergency department for a fever. His father states it has been as high as 104F at home, taken orally. It developed over the last couple of days and today the boy has been “loopy.” The father relates that the boy has spina bifida, and three weeks ago, he had a VP shunt placed after he suddenly regressed in physical therapy and was found to have hydrocephalus. At his first follow-up visit, he had regained his lower extremity motor function and had no complications from the surgery other than some minor pain.
You examine the boy and note a somnolent, but arousable, child in no acute distress. He has tactile warmth. He moans in pain when you flex his neck and you note an upgoing Babinski reflex. The rest of his exam is unremarkable. What are you most concerned for?
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Acute shunt infection
Acute shunt infection is a rare complication that occurs nearly exclusively in the immediate (weeks-months) post-implantation period. The advent of antibiotic-impregnated shunts and refined placement technique have decreased the incident of shunt infections. However, a high index of suspicion must be maintained as children may present with range of symptoms from generalized malaise and fever to acute reaccumulating CSF and increased ICP to frank meningitis.
Broad infectious workup should be initiated. A normal leukocyte count on CBC does not exclude a shunt infection, which may be localized. Other sources of infection should be excluded with chest x-ray, urinalysis and a thorough skin exam. Blood cultures should be obtained and broad-spectrum antibiotics/antivirals initiated. Most shunt infections are from skin flora such as Staphylococcus epidermis, S. aureus, and gram-negative rods. Consultation with neurosurgery is essential as these patients need source control in addition to standard antimicrobial therapy for meningitis or encephalitis.
Case 4
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You are working as solo coverage in a critical access hospital. After one-too-many people says “it sure is quiet tonight,” a mother comes rushing in with her 3-year-old child who appears to be minimally responsive and erratically breathing. After getting the patient on the monitor, you see her vital signs to be HR 75 bpm, BP 145/98 mmHg, RR 12, O2sat 84% on room air. She is arousable to painful stimuli only. After securing your ABCs, you get more history from the mother.
The child was born with a Chiari II malformation and required a VP shunt placement at 8 months of life. The shunt matured with minimal complications. Her mom takes her to see a neurosurgeon in clinic every 6 months for a check in and remarks “the closest option we had was 2 hours away.” She was doing well, but recently has had the “stomach flu” with a couple weeks of abdominal pain, nausea and vomiting.
You arrange interfacility transport and provide temporizing measures for what you suspect is an acute increase in ICP. Unfortunately, your helicopter is still 45 minutes away and the clinical picture is worsening. What can you do?
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Tap the shunt
This patient has likely developed an abdominal pseudocyst, which is a rare complication of peritoneal catheter placement. In the case of a distal shunt occlusion in the abdomen, tapping the shunt in the emergency department can be a life-saving maneuver. However, there are significant risks associated with the procedure and it should be reserved for cases with limited options or time, and under consultation of a neurosurgeon. Little data exists on the ideal emergent approach, but general concepts can be applied:
· Palpate the shunt reservoir, which will be cephalad/proximal either in cranium or neck
· Select an appropriate needle length for size of the child (reservoir will likely be just under the skin) with 22-25 gauge and, if possible, a three-way stopcock
· Proceed only in a sterile fashion (as we saw above, shunt infections are very real and deadly)
· Using analgesia and sedation as appropriate, access the reservoir with your needle tip and aspirate CSF, titrating to symptom management
· Collect CSF for laboratory evaluation if possible
In this case, you perform heroic measures and drain 40mL of CSF and the patient begins to stabilize. The secure the drain and close the three-way stopcock. Instructions on how to drain additional CSF are provided to the intrepid flight team when they arrive and the patient is whisked away to a tertiary care center with pediatric neurosurgery.
Post by Cody Stothers, MD PhD
Dr. Stothers is a PGY-1 in Emergency Medicine at the University of Cincinnati
Peer Editing by Carl Goff, MD and Ryan LaFollette, MD
Dr. Goff is a PGY-4 at the University of Cincinnati and Dr. LaFollette is an Associate Professor and Co-editor of TamingtheSRU
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