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NEUROCIRUGÍA
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Case report
Delayed spontaneous pneumocephalus inventriculoperitoneal shunting: Two case reports andliterature review
at the level of the frontal sinus was observed in the skull CT
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n e u r o c i r u g i a .
ntroduction
neumocephalus after shunting may be immediate, occur-ing in the first few days after shunt placement, or delayed,ppearing months or years following ventriculoperitoneal (VP)hunt insertion.1,2 This second scenario is more unusual and,ecause of the lack of a temporal relationship between theP shunt insertion and the pneumocephalus appearance,
he causal diagnosis may be much more elusive.We are reporting two new cases of delayed sponta-
eous pneumocephalus, which developed 1 and 5 years afterP shunt placement. We review the literature concerning
he physiopathology and management, as well as possiblepproaches to prevention of this condition.
ase reports
ase 1
65-year-old man with a history of subarachnoid hemor-hage secondary to right paraophthalmic aneurysm that wasreated endovascularly. The patient’s condition was compli-ated by a communicating hydrocephalus that required a VPhunt. One year later the patient was readmitted complain-ng of headache, drowsiness, gait disturbance and progressiveanguage impairment.
The cranial CT scan showed pneumocephalus in the frontalnd ventricular regions (Figs. 1 and 2). Further assessmentith high-resolution bone-window CT did not detect anyefects at the skull base.
The shunt was clamped and the pneumocephalus wasvacuated. Finally, a programmable anti-siphon valveas implanted, with the opening pressure set at 150 mmH2O.
Two weeks later the patient was discharged with residual
emiparesis but with complete resolution of the pneumo-ephalus (Fig. 3). There has been no recurrence during theollowing 18 months.
igs. 1 and 2 – Cranial X-ray and CT showing bifrontal tension pompression and midline shift.
pneumocephalus.
Case 2
A 64-year-old man, with a history of post-meningitis hydro-cephalus treated with ventriculoperitoneal shunt 5 yearspreviously (Fig. 4), was admitted to our department presentingwith headache, nausea, vomiting and seizures. A right frontalbasal pneumocephalus was observed in the CT scan (Fig. 5).The pneumocephalus was evacuated and the ventriculoperi-toneal shunt was removed due to infection.
After these procedures, a CT scan reconstruction of theskull and cisternography were carried out. Although no cere-brospinal fluid fistula was detected, a probable skull defect
neumocephalus causing significant ventricular
reconstruction (Fig. 6). Therefore, the anterior cranial fossawas examined surgically and the skull base defect was con-firmed and sealed.
88 n e u r o c i r u g i a . 2 0 1 4;2 5(2):86–89
Fig. 4 – Cranial CT scan after VP shunt placement.
Fig. 5 – CT scan shows a right fronto-basal tension
Fig. 6 – Bone CT reveals a small feature (arrow) that is asuspected cranial defect in right frontal skull base.
Fig. 7 – Three weeks later, the control CT illustrates
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pneumocephalus.
A programmable anti-siphon valve was implanted, withthe opening pressure set at 120 mmH2O. The tension pneumo-cephalus resolved completely and the patient was discharged3 weeks later with no new neurological deficit (Fig. 7).
Discussion
Spontaneous pneumocephalus related to a VP shunt hasbeen attributed to the coexistence of two conditions: thesiphon effect of a shunt diminishing intracranial pressure,and a skull base defect3–7 that permits the passing of airinto the cranial cavity. Specifically, the intracranial pressure
becomes lower than atmospheric pressure, and this allows airto enter the intracranial cavity (ball-valve theory).8 In cases inwhich the pneumocephalus appears early after VP placement,this process is evident to the neurosurgeon but, when the
resolution of the pneumocephalus.
complication develops months or years after the procedure,the cause may be not so easy to interpret.
Skull base defects may be congenital, but have most fre-quently been associated with meningeal-skull thinning anderosion, as a consequence of a long-lasting high intracra-nial pressure secondary to hydrocephalus.6 This condition hasbeen most commonly observed at the middle cranial fossa,4
which is understandable given its relatively thin bone struc-ture.
McCullough and Fox9 demonstrated excessive negativepressure in a high proportion of shunts performed. Theymeasured the pressure at the level of the foramen of Monroin supine, sitting and standing positions, reporting mean
changes ranging from −440 to −20 mmH2O. These alterationsin the pressure as a result of positional changes could bediminished using an anti-siphon device or high-pressure
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n e u r o c i r u g i a .
hunt,3,6 avoiding the excess in negative pressure in verticalostures and increasing the safety margin. The mechanismf early or immediate pneumocephalus associated with CSF
eaks is known as the “inverted bottle”; when CSF flows out, aegative pressure is created within the cranium and the space
iberated fills with air.Negative-pressure hydrocephalus could be the conse-
uence of a pressure gradient between the cortical subarach-oid space (CSAS) compartment and atmospheric pressureecause of a CFS leak that empties the cortical subarachnoidpace, in turn, creating a transmantle pressure of greater thanero that leads to ventriculomegaly. Transmantle pressure isefined as the differential pressure equal to the ventricularressure minus the CSAS pressure.10
The diagnostic criteria for low pressure hydrocephalusLPH) have been described by Pang and Alschuler.11 In hydro-ephalic patients with progressive ventriculomegaly andeurologic deterioration after shunting, a LPH should be sus-ected. These authors also describe how to treat this entity;rst and foremost, ventricular pressure must be substantiallyeduced with the objective of the decreasing the ventricularize. A less turgid and elastic brain with excessive complianceas been associated with this pathology.
The diagnosis of pneumocephalus can be made with a sim-le skull X-ray, but CT is the gold standard at present.12,13
ine-cut CT scans with three-dimensional reconstruction is valuable tool to locate skull base defects. However, the diag-ostic efficacy of CT cisternography is limited in the absencef an active CSF leak that is attributable to the “ball-valve”ffect: the air can get in but the contrast medium cannot getut, as occurred in our two cases.
Most authors agree that the first step in a tension pneu-ocephalus is the removal of intracranial air. In cases with
defect at the skull base, the treatment of choice is sealingf the defect by craniotomy or endoscopically. The pres-nce of a porencephalic cyst has been considered useful toetermine the region that requires surgical exploration whenhe defect is not evident.12,14 However, when the origin ofhe pneumocephalus is unknown, as in our first case, thepproach was first to remove the intracranial air followed byemporary shunt ligation and subsequent insertion of pro-rammable valve with anti-siphon device,15,16 to limit the CFSow through the shunt during Valsalva’s manoeuvres or vaso-enic ICP waves.
On the other hand, Filipidis et al.10 remind us that CSF leaksith pneumocephalus and low or negative pressure hydro-
ephalus may be refractory to standard surgical treatment. Inuch cases, Pang and Altschuler11 recommend treating withxtended periods of external ventricular drainage; Rekate17
onsiders that external drainage of CSF for long periods ofime with ICP maintained below the leak pressure level resultsn the healing of the leak. Another treatment option is neck
rapping, also proposed by Rekate,17 which serves to reversehe transmantle pressure and push more CSF through the ven-ricular drain, thereby decreasing ventricular size.
onclusion
elayed spontaneous pneumocephalus associated with VPhunt is a rare complication that can be attributed to the
1
;2 5(2):86–89 89
coexistence of a decrease in intracranial pressure generatedby the shunt (siphon effect) and the presence of a cranial-dural defect. If a porencephalic cyst is observed in CT scansof patients with VP shunts and a neurologic deterioration, weshould suspect the presence of and must search for a cranial-dural defect. Shunt devices with anti-siphon valves seem tobe useful in the treatment of tension pneumocephalus.
LPH should be suspected in cases of CSF leaks in patientswith ventriculomegaly and shunts malfunctions that do notimprove with shunt with the regular pressure.
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3. Barada W, Naijar M, Beydoun A. Early onset tensionpneumocephalus following ventriculoperitoneal shuntinsertion for normal pressure hydrocephalus: a case report.Clin Neurol Neurosurg. 2009;111:300–2.
4. Honeybul S, Bala A. Delayed pneumocephalus followingshunting for hydrocephalus. J Clin Neurosci. 2006;13:339–42.
5. Kawajiri K, Matsuoka Y, Hayazaki K. Brain tumorscomplicated by pneumocephalus following cerebrospinalfluid shunting-two case reports. Neurol Med Chir (Tokio).1994;34:10–4.
7. Tugcu B, Tanriverdi O, Gunaldi O, Baydin S, Postalci LS,Akdemir H. Delayed intraventricular tensionpneumocephalus due to scalp-ventricle fistula: a very rarecomplication of shunt surgery. Turk Neurosurg.2009;19:276–80.
8. Walker FO, Vern BA. The mechanism of pneumocephalusformation in patients with CSF fistulas. J Neurol NeurosurgPsychiatry. 1986;49:203–5.
9. McCullough DC, Fox JL. Negative intracranial pressurehydrocephalus in adults with shunts and its relationshipto the production of subdural hematoma. J Neurosurg.1974;40:372–5.
0. Filippidis AS, Kalani MY, Nakaji P, Rekate HL.Negative-pressure and low-pressure hydrocephalus: the roleof cerebrospinal fluid leaks resulting from surgicalapproaches to the cranial base. J Neurosurg. 2011;115:1031–7.
1. Pang D, Altschuler E. Low-pressure hydrocephalic stateand viscoelastic alterations in the brain. Neurosurgery.1994;35:643–55.
2. Hofmann E, Behr R, Schwager K. Imaging of cerebrospinalfluid leaks. Clin Neuroradiol. 2009;19:111–21.
4. Mylonas C. Delayed pneumocephalus in patients with CSFshunts. Br J Neurosurg. 1991;5:67–72.
5. Kim YH, Lee WI, Park MN, Choi HS, Kim NH, Han SJ. Otogenicpneumocephalus associated with a ventriculoperitonealshunt. Clin Exp Otorhinilaryngol. 2009;2:203–6.
