Neurovascular elements of the PCF

Transcription

1 Level I: Neurovascular elements of the PCF Trigeminal and Abducent Superior cerebellar artery and vein Dandy s vein Level II: Facial and Cochleovestibular AICA and internal auditory artery, veins Level III IX, X, XI PICA Level IV: Foramen magnum, XI, XII Vetebral, basilar and PICA NVCC Syndromes Trigeminal neuralgia Hemifacial Spasm Vertigo / Disabling positional vertigo (DPV) SNHL/ Tinnitus Glossopharyngeal neuralgia Vagal compression Brainstem compression

2 Pathophysiology Radiological evidence can be found 2-50% of the asymptomatic persons. Segmental demyelination by extrinsic compression by the vascular loop promotes, causing an ectopic synapse to occur (ephaptic or cross-talk transmission). The bioresonance hypothesis states that when the vibration frequency of a structure surrounding the trigeminal nerve becomes close to its natural frequency, the resonance of the trigeminal nerve occurs causing myelin damage Diagnosis Clinical picture: Usually confused with other diseases Mass effects without a mass Radiological studies: Mainstay of diagnosis Misleading if not properly conducted Radiological evidence can be found 2-50% of the asymptomatic persons. 2

3 Imaging Modalities High resolution CT scan CT angiography HR MRI 3D fast spin echo (FSE) 3D fast gradient echo (FGRE) technique 3D FSE (Driven equilibrium (DRIVE) 3D balanced fast-field echo (bffe) 3D-FT T2-weighted (CISS) MR angiography Normal Vascular Anatomy Axial plane Coronal plane 3

4 MRA MRV Patients and Methods 48 patients : 27 males and 2 females ( 27-6 years, mean 45 years ) Clinical picture Trigeminal neuralgia Number 6 HFS 2 Tinnitus / SNHL /DPV 29 Glossopharyngeal neuralgia 4

5 Methods Technique:- Axial and coronal thin special T2W images Axial TW thin cuts for the temporal bones Axial T2 WI for the brain. 3 D balanced fast field echo (3D BFFE) 3D driven equilibrium (DRIVE). T 2 3D BFFE clear, T2 3D drive clear and FSE images : -CSF hyperintense. -Nerves and vessels hypointense. T 3D FFE clear revealed blood vessels hyperintense. Evaluation The following structures were evaluated: Cranial nerves. Vascular anatomy at CPA and VBA Offending VCC. Visualization was graded : 2 3 if an anatomical structure was not visible, a visible anatomical structure with only minor artifacts anatomical structure was clearly visible with no artifacts. VCC = the nerve and the vessel were inseparable by an identifiable CSF cleft in two of three orthogonal planes. VCC was characterized into 4 types: Type point compression Type 2 longitudinal compression Type 3 loop compression Type 4 indentation 5

6 CT scan with contrast at the level of IAC. Only the sigmoid sinus is seen without evident details of the NVS of CPA. MRI Left HFS 6

7 Axial T2 3D BFFE MRI Left HFS Axial T2 3D drive MRI 7

8 FSE Type vascular loop Axial T2 3D drive clear MRI 8

9 Suspected Vessel by MRI Clinical picture Number Vessel Number TG Neuralgia 4 SCA 3 HFS Vestibulocochlear Glossopharyngeal 0 28 AICA VBA PICA AICA PICA PICA Endoscopic findings of surgically explored patients (45) Clinical picture HFS Trigeminal Neuralgia Vestibulocochlear Number AICA VBA PICA Pontine Vein SCA Dandy s vein Endoscopic findings AICA AICA (not compressing). PICA VBA 9

10 Vessel MRI Surgery Vestibulocochlear AICA AICA (-ve) 2 PICA VBA 0 2 Hemifacial spasm AICA 5 5 PICA VBA 4 3 Vein Trigeminal Neuralgia SCA 3 3 Dandy s vein Type of Compression Type Number I 9 II 6 III 9 IV 5 Undetermined 9 0

11 TN and Type 2 compression Hemifacial spasm and Type 3 loop

12 Type AICA causing SNHL Axial 3D BFFE Type 2 AICA loop 2

13 DPV due to a type 4 loop Glossopharyngeal neuralgia Type 4 PICA loop 3

14 Axial T2 3D bffe MRI HFS: double conflict Axial T2 3D DRIVE : Type 3 loop between the nerves 4

15 Axial T2 3D drive AICA Type loop Left HFS AICA and adhesion around AFB 5

16 Conclusions T2 MRI high resolution 3D bffe, T2 3D drive clear can accurately delineate the neurovascular relationship in CPA The NV conflict could be demonstrated in 43/48 scanned patients (89.58%) 3D drive clear was superior to 3D bffe in outlining the conflicts The pre-operative presumptive vessel was correct in 38/42 operated cases (90.4%) No venous conflicts could be detected by either technique. The type of compression could be accurately predicted in all cases. Conclusion In suspected NVCCS preoperative MRI can accurately outline the conflict. However the proper technique should be requested as routine techniques can be misleading. Non-contrast T2 HRMRI 3D bffe, T2 3D drive clear and FSE can delineate the neurovascular relationship in CPA. 3D DRIVE clear has the highest yield and should be the study of choice in such cases 6