| Objective1. To investigate the relationships between transhorizontal cerebellopontinefissure and trigeminal nerve, cerebellar artery(CA), petrosal vein(PV);2. To quantitatethe anatomical datum before/after the transhorizontal cerebellopontine fissure beenseparated;3. To measure the distances between transhorizontal cerebellopontinefissure and root entry zone(REZ), PV, CA;4. To measure the distances between REZand CA, PV;5. To investigate the relationships between PV and its adjacent structures;6. To statistical analysis all the measured datum, in order to provide the evidence ofneurosurgical therapy for trigeminal neuralgia.MethodsThe systems of artery and vein from10fresh cerebullar specimens of adults hadbeen perfused with the red and bule lactoprene respectively for a week, then:1.simulate the operative route of the transhorizontal cerebellopontine fissure approachunder the operating microscope: lateral decubitus position and posterior-mastoidincision was taken, drill a hole on the skull with a diameter3.0cm, incise the dura atthe intersection of sigmoid sinus and transverse sinus, measure the distance betweenthe ultima thule of the operating field and the intersection of sigmoid sinus andtransverse sinus before/after the transhorizontal cerebellopontine fissure beenseperated;2. exposion of the cerebellum: incise skin, skull along the line of geisoma,zygomatic arch, external acoustic foramen, superior nuchal line and external occipitalprotuberance, remove the dura and cerebrum one the plane of cerebral peduncle, incisethe tentorium of cerebellum along the line of petrous bone and superior petrosal sinus,observe the relationships between superior petrosal sinus, trunk/branches of pretrosalvein and root of trigeminal nerve; expose REZ to investigate and measure thedistances between transhorizontal cerebellopontine fissure and CA, pretrosal vein, trigeminal nerve; cut the nerves and vessels which rooted in the brain stem one by one,take out the brain stem and cerebellum, investigate and take pictures local structure.Results1. The influence of separated transhorizontal cerebellopontine fissure on theexposion of operating field.1.1The distance between ultima thule of the operating field and intersection ofsigmoid sinus and transverse sinus before the transhorizontal cerebellopontine fissurebeen seperated was (3.20±1.11)mm;1.2The distance between ultima thule of the operating field and intersection ofsigmoid sinus and transverse sinus after the transhorizontal cerebellopontine fissurebeen seperated was (18.65±3.75)mm, increased remarkably(P＜0.01);1.3The exposion of REZ was ameliorated well after transhorizontalcerebellopontine fissure been seperated;2. The adjacent structure of transhorizontal cerebellopontine fissure.2.1Datum of the separated fissure: length (30.00±3.60)mm; depth(11.50±1.99)mm;2.2Datum of the separated fissure’s upper limb: length (20.65±2.41)mm; depth(7.40±1.96)mm;2.3The distance of transhorizontal cerebellopontine fissure from the trunk ofpretrosal vein (13.63±1.59)mm; from the superior cerebellar artery(SCA)(15.80±7.26)mm; from the anterior inferior cerebellar artery(AICA)(18.35±6.25)mm;from the posterior inferior cerebellar artery(PICA)(23.00±1.49)mm;3. Microdissection of PV.3.1Branches of PV:2in20sides had double trunks;7sides had2branches(31.8%);11sides had3branches(50.0%);4sides had4branches(18.2%);3.2The relationship between PV and inner auditory meatus(IAN):40.9%insideof the IAN;27.3%above on the IAN;31.8%outside of the IAN;3.3The relationship between PV and the root of trigeminal nerve:86.4%trunksof PV located dorsolateral side to the root of trigeminal nerve;13.6%trunks of PVlocated ventrolateral side to the root of trigeminal nerve;13.6%trunks and15.7%branches of PV contacted with REZ, and4.6%trunks and3.9%branches of PVoppressed REZ, all the branches were pontile transverse veins;3.4The length of the trunks of PV:(2.73±1.83)mm; length range from0.52mm to 8.29mm;3.5The distance between PV and REZ:(13.10±4.10)mm, range from3.67mm to19.79mm; the distance between untouched trunk of PV and REZ:(5.64±1.68)mm,range from1.73mm to23.32mm; the distance between PV and intersection of sigmoidsinus and transverse sinus:(31.40±5.59)mm, range from20.53mm to42.12mm;4. Microdissection of trigeminal nerve.4.1Anatomical characteristics of brainstem section and cistern section oftrigeminal nerve: all the cases can expose REZ well after the transhorizontalcerebellopontine fissure been separated, and the operation can be completed;4.2The relationship between trigeminal nerve and vessels: REZ contact withvessels in17sides(10cases in left sides,7cases in right sides); the contacting vesselswere: SCA3cases, SCA+PV2cases, SCA+branches of PV3cases,SCA+AICA+branches of PV1cases, AICA+branches of PV3cases, AICA+PV1cases, PV1cases, branches of PV3cases;4.3Blood supply of trigeminal nerve: the feeding arteries of trigeminal nerve rosefrom basilar artery mostly, such as SCA, AICA.100%of AICA participated in theblood supply of trigeminal nerve, and,30%of SCA took part in it;4.4The distances of REZ from transhorizontal cerebellopontine fissure were(19.55±2.16)mm;Conclusions1. It is operable to the microvascular decompression for the treatment oftrigeminal neuralgia through the transhorizontal cerebellopontine fissure approach.That could protect the trunks and the large branches of the petrosal veins that block theoperative route, expose of fhe root entry zone of trigeminal nerve more sufficiently,decompress trigeminal nerve more completely;2. REZ can be exposed well after transhorizontal cerebellopontine fissure beenseparated;3. PV is blamed for the trigeminal neuralgia sometimes, and is the roadblock forthe operation. How to handle PV is the key point of the operation;4. SCA should be responsibility for trigeminal neuralgia mostly; AICA is themain feeding artery of trigeminal nerve;5. The research enrich anatomic content for the zone of cerebellopontine angle. |
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