Extracranial aneurysms of the posterior inferior cerebellar artery

Association of a Distal Intradural-Extracranial Posterior Inferior Cerebellar Artery Aneurysm With Chiari Type I Malformation

BACKGROUND AND IMPORTANCE:

Distal extracranial posterior inferior cerebellar artery (PICA) aneurysms are very rare lesions and have not been previously reported in association with a Chiari type I malformation (CMI).

CLINICAL PRESENTATION:

A 56-year-old woman with a distal, low-lying, intradural-extracranial PICA aneurysm presented with a subarachnoid hemorrhage and was treated with coil embolization. The patient presented again 1 month later with symptoms of a CMI and was found to have tonsillar herniation and a large syrinx that appeared to be exacerbated by the coil mass. The patient was re-treated with a suboccipital craniectomy, C1-2 laminectomy, aneurysm trapping and excision, end-to-end PICA anastomosis, and expansile duraplasty.

CONCLUSION:

Although just a single case, important teaching points regarding the angiographic appearance of a CMI and treatment options for distal PICA aneurysms that are situated below the foramen magnum can be learned. A low-lying caudal PICA loop should trigger a workup for a CMI. Caution should be taken when using coil embolization for aneurysms in the high cervical spinal canal. Bypass with aneurysm trapping and excision may be a superior treatment option in these cases because the posterior fossa and high cervical canal can be concomitantly decompressed. To our knowledge, this is the only case reported of a distal intradural-extracranial PICA aneurysm associated with a CMI.

Extracranial aneurysms of the distal posterior inferior cerebellar artery: Resection and primary reanastomosis as the preferred management approach

Background:

Extracranial aneurysms of the posterior inferior cerebellar artery (PICA) are rare, with only 22 reported cases in the English literature. For saccular extracranial distal PICA aneurysms not amenable to coiling, a surgically placed clip is not protected by the cranium postoperatively, and can be subject to movement in the mobile cervical region. Furthermore, fusiform or complex aneurysms cannot be clipped primarily. Resection and primary reanastomosis is a useful surgical approach not previously described for these extracranial lesions.

Case Description:

We report three cases of extracranially located distal PICA aneurysms successfully treated with this surgical strategy at our center. One patient harboring a broad necked saccular aneurysm originally underwent successful primary clipping of the aneurysm but sustained a second subarachnoid hemorrhage (SAH) on postoperative day 25 due to clip dislodgement from vigorous neck movement. The other two patients were found to have fusiform and complex aneurysms, respectively. All three patients were ultimately treated with resection and end-to-end PICA anastomosis, which successfully obliterated their aneurysms.

Conclusions:

Resection and primary reanastomosis of extracranial distal PICA aneurysms averts the risk of clip dislodgement due to neck movement and/or compression by soft tissues in the upper cervical region. It is a safe and efficacious technique, which we propose as the preferred management strategy for these rare vascular lesions.

Surgical Management of PICA Aneurysm and Incidental Facial Nerve Schwannoma: Case Report

We report a patient with a posterior inferior cerebellar artery (PICA) aneurysm and an incidental facial nerve schwannoma at the cerebellopontine angle (CPA). A 46-year-old woman presented with the sudden onset of a severe headache, nausea, and vomiting. She had no other abnormal neurological symptoms and signs. Computed tomography (CT) showed hemorrhage in the fourth ventricle. Cerebral angiography demonstrated an aneurysm arising from the tonsillomedullary segment of the left PICA. A facial nerve schwannoma was incidentally found as the aneurysm was being clipped. The aneurysm was clipped via a left transcondylar approach. Subsequently, the schwannoma (2 x 3 x 2 mm) was resected from the facial nerve fascicles, and the facial nerve was preserved. Postoperatively, the patient developed mild to moderate dysfunction of the facial nerve (House-Brackmann grade III [H-B III]) but her hearing was intact. Both a facial nerve schwannoma involving the CPA and an aneurysm involving the PICA can be managed through the transcondylar approach. An asymptomatic facial nerve schwannoma can be resected safely with minimal facial nerve dysfunction.

Extracranial aneurysm of the distal PICA presenting as isolated fourth ventricular hemorrhage: case report and literature review

BACKGROUND

Posterior inferior cerebellar artery (PICA) aneurysms are relatively uncommon, comprising only 0.5-3% of all intracranial aneurysms. Distal PICA aneurysms are much more uncommon, with more than 200 cases being reported in the literature. The finding of an extracranially located aneurysm of distal PICA is considered a true rarity.

METHODS AND DISCUSSION

A rare case of extracranially located PICA aneurysm presenting with isolated fourth ventricular hemorrhage is presented and the diagnostic and therapeutic challenges discussed.

Subarachnoid hemorrhage caused by ruptured dissecting aneurysm arising from the extracranial distal posterior inferior cerebellar artery--case report

A 50-year-old man presented with a dissecting aneurysm arising from the extracranial portion of the right posterior inferior cerebellar artery (PICA) causing subarachnoid hemorrhage (SAH) and manifesting as sudden onset of disturbed consciousness. Computed tomography showed SAH with ventricular reflux predominantly in the posterior fossa. Angiography revealed a fusiform aneurysm of the right PICA originating extracranially from the right vertebral artery. The aneurysm was isolated and excised. Histological examination showed dissection of the aneurysm wall. Dissecting aneurysm arising from the extracranial portion of the PICA is extremely rare.

Blink reflexes in chronic tension-type headache patients and healthy controls

OBJECTIVE

To use the R2 component of nociceptive-specific blink reflex (nBR) to probe the trigeminal nociceptive system and compare chronic tension-type headache (CTTH) patients and healthy controls.

METHODS

Thirty patients with CTTH and 30 age- and sex-matched healthy control subjects were included. nBR were evoked by painful electrical pulses (0.5ms duration), delivered by a concentric electrode placed on the left lower forehead close to the supraorbital foramen. The EMG activity in the orbicularis oculi muscles was recorded bilaterally. The electrical stimulus intensities to evoke individual sensory threshold (Is) and pin-prick pain sensation (Ip) were assessed. A fixed stimulation intensity of 1.5x Ip was used to evoke the nBR. The perceived pain intensity of the electrical stimulus (I(BR)) was assessed by the subjects on a 0-10cm visual analogue scale (VAS).

RESULTS

Is did not differ between CTTH patients and controls (P=0.687) but were lower in females than in males (P=0.020). CTTH patients had higher scores on I(BR) than controls (P=0.026). ANOVA showed significantly higher pre-stimulus EMG values in CTTH patients on the left (stimulated) side (P<0.001), whereas there were no differences between males and females (P>0.168). There were no significant differences in the absolute values of the nBR, however CTTH patients had significantly lower values of the normalized root mean square (RMS) (P=0.035) and area under the curve (AUC) (P=0.042) of the nBR on the left side compared with control subjects with no sex-related differences (P>0.070). The onset latencies and duration were not significantly different between CTTH and control subjects or between female and male subjects (P>0.270). There was no significant correlation between any of the BR parameters (RMS, AUC) and clinical characteristics of CTTH (headache intensity and duration) (P>0.163).

CONCLUSIONS

The results of the present study did not detect a significantly different blink reflex response in CTTH patients, but suggested that painful electrical stimulation was associated with consistent increases in eye muscle activity on the same side.

SIGNIFICANCE

These findings add further information to central nociceptive pathways in CTTH patients.

Surgical management of ruptured and unruptured symptomatic posterior inferior cerebellar artery aneurysms

This retrospective study analyses the outcome of posterior inferior cerebellar artery aneurysms treated surgically. Thirteen consecutive ruptured and unruptured PICA aneurysm patients from January 1998 to January 2004 were reviewed retrospectively. The mean age was 49.1 +/- 7.4 years. Three were unruptured aneurysms and ten presented with acute subarachnoid haemorrahge. Surgery was performed immediately after completed 4 vessel angiograms using the far lateral approach. Eight were fusiform while five were saccular aneurysms. The saccular aneurysms were clipped. Treatment of the fusiform aneurysms included 3 trappings and three proximal clippings. One patient refused surgery and had endovascular occlusion of a giant PICA aneurysm. Eight out of ten (80%) operated patients needed CSF shunting for hydrocephalus. All check angiograms during follow up demonstrated adequate exclusion of the aneurysms from the circulation. None developed the PICA syndrome clinically or showed infarction on brain scans. All good grade patients recovered without neurological deficits. Our experience showed that early surgery for ruptured PICA aneurysm carries a good prognosis with low morbidity. In aneurysms that cannot be clipped, sacrifice of the PICA without revascularisation procedures in proximally located PICA aneurysms may still be feasible if the occlusion is done distal to the perforators.

Extracranial aneurysm of the posterior inferior cerebellar artery with an aberrant origination: case report

OBJECTIVE

Aneurysms of the extracranially originating posterior inferior cerebellar artery are very rare. An anatomic insight of its possible course and variations is necessary when confronting such extraordinary lesions.

CLINICAL PRESENTATION

A 19-year-old man presented with the sudden onset of severe headaches. A physical examination was positive only for neck rigidity. Computed tomographic scans of the brain depicted intraventricular hemorrhage. TECHNIQUE AND INTERVENTION: Four-vessel brain digital subtraction angiography revealed an extracranial posterior inferior cerebellar artery arising extradurally from the right vertebral artery between the C1 and C2 vertebrae, bearing a saccular aneurysm in an upper cervical intradural location. An anterior inferior cerebellar artery-posterior inferior cerebellar artery variant was also found on the left side. Computed tomographic angiography failed to unmask the lesion. The aneurysm was clipped through a suboccipital craniectomy and C1 laminectomy.

CONCLUSION

The patient did well after surgery and was discharged from the hospital without neurological deficit. One can conclude that a comprehensive diagnostic approach oriented to the patient history and clinical data is mandatory to preclude such lesions evading the vigilant surgeon.

Posterior inferior cerebellar artery with extracranial origin harboring an extracranial aneurysm

BACKGROUND

We report on a rare case of a saccular aneurysm on the TM segment of the right PICA. The aneurysm was located at the nonbifurcation region of the PICA.

CASE DESCRIPTION

The patient underwent a brain CT scan that revealed a diffuse SAH and an IVH in the fourth ventricle with obstructive hydrocephalus. After external ventricular drainage to relieve the hydrocephalus, the aneurysm was demonstrated by cerebral digital subtraction angiography.

CONCLUSIONS

The origin of the PICA aneurysm was extracranial and intradural, illustrating a rare location of such type of aneurysm.

Extracranial aneurysm of the posterior inferior cerebellar artery

Aneurysms of the posterior inferior cerebellar artery (PICA) are rare, and may arise in unusual locations due to the complex and variable anatomy of this artery. The PICA does not usually originate from the extracranial vertebral artery. Of the few reported extracranial PICA aneurysms, all affected the distal segment. We describe an unusual extracranial PICA-vertebral artery (VA) junction aneurysm.

Functional connectivity between trigeminal and occipital nerves revealed by occipital nerve blockade and nociceptive blink reflexes

Headache syndromes often suggest occipital and neck involvement, although it is still unknown to what extent branches of segment C1-C3 contribute actively to primary headache. Pain within the occipital area may be referred to the trigeminal territory. However, a modulation of trigeminal transmission by affecting cervical input in humans has not been elucidated so far. A convergence of cervical and trigeminal input at the level of the caudal part of the trigeminal nucleus in the brainstem has been suggested due to anatomical and neurophysiological studies in animals. We examined the R2 components of the nociceptive blink reflex responses in 15 healthy subjects before and after unilateral nerve blockade of the greater occipital nerve with 5 ml prilocain (1%). R2 response areas (AUC) decreased and the R2 latencies increased significantly after the nerve blockade only on the side of injection. AUC and latencies on the non-injection side remained stable. Thresholds for sensory or pain perception did not differ significantly between the repeated measurements on both sides. Our findings extend previous results related to anatomical and functional convergence of trigeminal and cervical afferent pathways in animals and suggest that the modulation of this pathway is of potential benefit in primary headache disorders.

Distal posterior inferior cerebellar artery aneurysms: clinical features and management

OBJECT

Aneurysms located on the distal portion of the posterior inferior cerebellar artery (PICA) are uncommon, and their underlying pathology, natural history, and clinical management are poorly understood. To clarify these lesions more fully, the authors undertook a retrospective analysis of the clinical features and management results of 22 distal PICA aneurysms in 20 consecutive patients treated at one institution by the same surgeon during the past decade.

METHODS

The series included 10 men and 10 women (mean age at presentation 51 years). Nine patients presented with only subarachnoid and/or intraventricular hemorrhage (median Hunt and Hess Grade II). In seven patients intracerebellar hemorrhage was also found; two patients presented with pressure effects and two hemorrhages were incidentally discovered. Prominent comorbidities included cigarette smoking (50%) and hypertension (50%). The 13 saccular and nine fusiform distal PICA aneurysms were distributed on the following segments of the PICA: lateral medullary (seven lesions), tonsillomedullary (five lesions), telovelotonsillar (five lesions), and cortical (five lesions). Six oases were associated with cerebellar arteriovenous malformations. Skull-base and far-lateral transcondylar surgical approaches were used to secure the aneurysms in 86% of cases, either by direct clipping (13 lesions), vessel sacrifice (four lesions), or vessel sacrifice plus bypass (two lesions). Two aneurysms were treated using endovascular PICA ablation. Overall outcome at hospital discharge was excellent or good in 70% of cases. At long-term follow up (100% of patients, mean 123 days), an excellent or good outcome had been achieved in 85% of cases.

CONCLUSIONS

Depending on the PICA segment that was affected, variations in clipping strategies and surgical exposures aimed at the PICA branch and main trunk preservation were major contributors to good long-term results.

Successful clipping of a distal posterior inferior cerebellar artery aneurysm located on the anterior surface of the medulla oblongata--case report

A 55-year-old male presented with a ruptured distal posterior inferior cerebellar artery (PICA) aneurysm manifesting as subarachnoid hemorrhage. Angiography demonstrated a saccular aneurysm arising from the lateral medullary segment of the left PICA and located on the medial side of the left vertebral artery (VA) and the anterior surface of the medulla oblongata. A transcondylar fossa approach was used to ensure a sufficient operating field and to obtain adequate visualization of the aneurysm, the parent artery, and the perforating arteries to the medulla oblongata. The aneurysm dome protruded medially at the hairpin curve, and was located on the medial side of the left VA and on the anterior surface of the medulla oblongata. There was no vessel branches in the vicinity of the aneurysm. The aneurysm was successfully clipped with minimum retraction of the cerebellar hemisphere and medulla oblongata. Distal PICA aneurysms can be located at various sites in the posterior fossa. The exact location of the aneurysm must be established to select the best surgical approach.