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Turkish Neurosurgery 2007, Vol: 17, No: 1, 37-39

Burçak B‹LG‹NER

‹brahim M. Z‹YAL

Özgür ÇEL‹K

Selim AYHAN

Nejat AKALAN

Department of Neurosurgery, Hacettepe University School of Medicine,Ankara, Turkey

Received : 15.02.2007Accepted : 04.03.2007

Correspondence Address Burçak B‹LG‹NERHacettepe University School of Medicine,Department of Neurosurgery,06100, Sihhiye, Ankara, TurkeyPhone: +90 312 3051715Fax : +90 312 3111131E-mail : burcak@tr.net

Enlargement ofPostoperative AqueductalAir Due to Elevated BodyTemperature Case Report

ABSTRACTPneumocephalus has been reported after posterior fossa surgery especially withprocedures performed in the sitting position. The gravitational effect is thedecisive factor in the development of pneumocephalus. The entrapped air in theaqueduct may enlarge due to several factors such as elevated body temperatureand may cause to deterioration in neurological status. We report a rare case of tension pneumocephalus associated with theenlargement of massive air in aqueduct due to elevated body temperature,following removal of a cervicomedullary tumor. We believe her neurologicaldeterioration was due to the compression of the reticular formation bydilatation of postoperative air in the aqueduct due to the elevation of her bodytemperature.KEY WORDS: Tension pneumocephalus, Aqueduct, Posterior fossa surgery.

INTRODUCTIONPneumocephalus is a postoperative complication fre q u e n t l y

encountered in neurosurgery.Postoperative pneumocephalus was first reported by Markham in

1967 (3). Tension pneumocephalus has been frequently observed afterposterior fossa surgery, especially in procedures performed in thesitting position. In a retrospective study, the incidence of intracranial aircollection was 100% in the sitting position (2). The sitting position inneurosurgical operations achieves an optimal access to lesions situatedin the midline and drainage of the cerebrospinal fluid (CSF). In allposterior fossa explorations performed in the sitting position, there isalways some degree of pneumocephalus. This position promotes thedrainage of CSF from the intracranial cavity with a resultant entry of airin a process similar to that observed with an inverted pop bottle (1). Airmay enter via the fourth ventricle into the aqueduct. The enlargementcapacity and elasticity of the aqueduct re g a rding tensionpneumocephalus is limited. In our opinion, the volume of a sealed gas-filled compartment may increase in size and expand the aqueduct withelevation of the body temperature. This expansion may causeneurological deterioration following compression of the brain stem.

Here, we present a case who developed tension pneumocephalus atthe aqueductus slyvii with deterioration in neurological statusfollowing elevated body temperature after removal of acervicomedullary tumor.

CaseA 1 4 - y e a r-old girl presented with a 2-week history of gait disturbance

and imbalance. Neurological examination revealed ataxia, dysmetry,

dysdiadokokinesia and bilateral end-pointnystagmus. Magnetic resonance imaging (MRI) scansrevealed a cervicomedullary junction mass lesion( F i g u re 1). Early postoperative MRI showed gro s stotal tumor removal with air in the fourth ventricleand some air in the aqueduct (Figure 2). Her bodyt e m p e r a t u re increased to 39.8 degrees Celsius 3 daysafter the operation and she became unconscious andagitated. Early postoperative computed tomography(CT) scan revealed enlargement of aqueduct that wasassociated with triventricular hydrocephalus. Sheunderwent a shunt pro c e d u re for her hydro c e p h a l u s ,but the shunt pro c e d u re did not improve hern e u rological status. Her neurological statusi m p roved as her fever subsided and the follow-upC Ts showed that the air in the aqueduct wasabsorbed in three weeks (Figure 3).

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Turkish Neurosurgery 2007, Vol: 17, No: 1, 37-39 Bilginer: Enlargement of Postoperative Aqueductal Air Due to Elevated Body

DISCUSSIONThe aqueduct of sylvius is a pathway connecting

the posteroinferior third ventricle to the superioraspect of the fourth ventricle. The cerebral aqueductis more dilated in the embryonic brain than in them a t u re brain. After the initial closure of the neuraltube, its lumen has a relatively uniform dimensiont h roughout the neural axis. As the brain and spinalc o rd mature, the lumen of the neural tube expands insome areas, such as the cerebral ventricles, andn a r rows in others, such as the sylvian aqueduct. Thelumen of the aqueduct decreases in size, beginning inthe second month of fetal life and continuing untilbirth. This narrowing appears to be caused by gro w t hp re s s u res upon the aqueduct from adjacentmesencephalic stru c t u res (4). The normal mean cro s s -sectional area of the aqueduct at birth is 0.5 mm2 witha range of 0.2 mm2 to 1.8 mm2. The size of aqueductis focally reduced in aqueductal stenosis and thestenosis usually occurs either at the level of thesuperior colliculi or at the intercollicular sulcus (5).

Tension pneumocephalus is a distinct clinicalentity necessitating active intervention. Te n s i o npneumocephalus is most commonly subdural and

Figure 1: 14-year-old girl with a posterior fossa tumorA) Axial postcontrast T1-weighted MR image B) Coronalpostcontrast T1-weighted MR image.

Figure 2: Postoperative aqueductal pneumocephalus wasseen after gross total removal of the posterior fossa tumorA) Axial T1-weighted MR image B) Coronal T1-weightedMR image.

1A 1B

2A 2B

Figure 3: CT scans showed large aqueductal collection andresorption of air in 3 weeks A) Postoperative 3rd day whenthe elevation of her body temperature was maximal.B) Postoperative 5th day C) 2 weeks after the operationD) 3 weeks after the operation.

3A 3B

3C 3D

bifrontal, but may occur in the fourth ventricle andaqueduct. It occurs as a result of the drainage of CSFby gravity, producing negative pre s s u re in thesupratentorial compartment and thus allowing air toenter, ascend and collect. Tension pneumocephalusmay present as deterioration of consciousness withor without lateralizing signs.

There is still controversy on the surgical positionfor posterior fossa lesions. Some advantages of thesitting position include no accumulation of blood inthe surgical field and continuous drainage of CSFduring the operation. However, this position hasdrawbacks like venous air embolism and tensionpneumocephalus. On the other hand, the risk ofpneumocephalus in the prone position is almost 0%.Both position are currently used depending on thesurgeon's choice, and there is no obvious advantageof one position over the other.

The entrapment of massive air in the aqueducto b s t ructed the CSF pathway and resulted inhydrocephalus in our case. The patient underwent ashunt procedure, but the neurological condition did

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Turkish Neurosurgery 2007, Vol: 17, No: 1, 37-39 Bilginer: Enlargement of Postoperative Aqueductal Air Due to

not improve. We believe her neuro l o g i c a ldeterioration was due to the compression of thereticular formation by the dilatation of postoperativeair in the aqueduct following elevation of her bodytemperature. Her neurological status improved oncethe body temperature decreased to normal. She wasd i s c h a rged with total recovery and no air inaqueduct after three weeks.

REFERENCES1. Palazon J.H, Martinez-Lage J.F, De La Rosa-Carrillo V.N,

Tortoza J.A, Lopez F, Poza M. 2003. Anesthetic technique anddevelopment of pneumocephalus after posterior fossa surgeryin the sitting position. Neurocirugia. 14:216-221

2. Prabhakar H, Bithal K.P, Garg A. 2003. Te n s i o npneumocephalus after craniotomy in supine position. JNeurosurg Anesthesiol. 15(3):278-281

3. Suri A, Mahapatra A.K, Singh V.P. 2000. Posterior fossa tensionpneumocephalus. Child’s Nerv Syst. 16:196-199

4. Turkewitsch N. 1935. Die entwicklund des aquaeductuscerebri des menschen. Morphologisches Jahrbuch. 76:421-477

5. Woollam DHM, Millen JW. 1953. Anatomical considerations inthe pathology of stenosis of the cerebral aqueduct. Brain.76:104-112