The normal anterior inferior cerebellar artery. Anatomic-radiographic correlation with emphasis on the lateral projection

The Anterior Inferior Cerebral Artery Variability in the Context of Neurovascular Compression Syndromes: A Narrative Review

The anterior inferior cerebellar artery (AICA) is situated within the posterior cranial fossa and typically arises from the basilar artery, usually at the pontomedullary junction. AICA is implicated in various clinical conditions, encompassing the development of aneurysms, thrombus formation, and the manifestation of lateral pontine syndrome. Furthermore, owing to its close proximity to cranial nerves within the middle cerebellopontine angle, AICA's pulsatile compression at the root entry/exit zone of cranial nerves may give rise to specific neurovascular compression syndromes (NVCs), including hemifacial spasm (HFS) and geniculate neuralgia concurrent with HFS. In this narrative review, we undertake an examination of the influence of anatomical variations in AICA on the occurrence of NVCs. Significant methodological disparities between cadaveric and radiological studies (CTA, MRA, and DSA) were found, particularly in diagnosing AICA's absence, which was more common in radiological studies (up to 36.1%) compared to cadaver studies (less than 5%). Other observed variations included atypical origins from the vertebral artery and basilar-vertebral junction, as well as the AICA-and-PICA common trunk. Single cases of arterial triplication or fenestration have also been documented. Specifically, in relation to HFS, AICA variants that compress the facial nerve at its root entry/exit zone include parabola-shaped loops, dominant segments proximal to the REZ, and anchor-shaped bifurcations impacting the nerve's cisternal portion.

[A Case of Hearing Loss Preceding Anterior Inferior Cerebellar Artery Infarction Syndrome With a Progressive Course]

Anterior inferior cerebellar artery (AICA) syndrome is a well-known symptomatic disorder. AICA syndrome is one of the causes of sudden hearing loss seen in recent years, but most of these cases were diagnosed as hearing loss preceded by other symptoms. Due to variations in AICA, we consider that many cases are actually not recognized as AICA syndrome. In this report, we describe a case of AICA syndrome preceded by hearing loss and describe its course of progression.

Onyx embolization of a ruptured anterior inferior cerebellar artery in a neonate

Aneurysmal subarachnoid hemorrhage (SAH) is rare in neonates. The authors present a unique report of a neonate with SAH from anterior inferior cerebellar artery (AICA) aneurysm rupture that was successfully treated with Onyx embolization. This case report demonstrates the utility of Onyx embolization for posterior circulation aneurysms in neonates and the successful management of SAH in this population.

Vascular Anomalies of Posterior Fossa and Their Implications

Posterior fossa houses very vital and sensitive structures namely midbrain, pons, medulla, and cerebellum. These structures are irrigated by vertebral, posterior inferior cerebellar, anterior inferior cerebellar, and superior cerebellar arteries. Parts of brain located in posterior fossa control important parts of body so any variation pertaining to stenosis, atresia, hypoplasia, fenestration, agenesis, and duplication in the arteries supplying these parts alter the irrigation pattern culminating into various morbid and mortal neurologic disorders. Therefore, a sound understanding and thorough knowledge of posterior circulation vascular variant anatomy builds the foundation for the accurate diagnosis and appropriate management of neurovascular ischemic and hemorrhagic diseases of posterior fossa. To aid in addressing these complex neurologic disorders and neurosurgical treatment to be carried out successfully, updating and consolidating the knowledge of all the variations/insults of these arteries becomes essential. Therefore, review study has been carried out.Literature search was carried out using databases, including Scielo, Scopmed, Medline, PubMed, and Wiley online library. Papers containing original data were selected and secondary references retrieved from bibliographies. Search terms used were posterior fossa, anomalies of vertebral, posterior inferior cerebellar, anterior inferior cerebellar, and superior cerebellar arteries.The study will be of paramount importance to angiographers in interpreting angiographs, neurologists in diagnosis and treatment of neurologic disorders, and neurosurgeons in performing surgery in posterior fossa and craniovertebral region particularly dealing with tumors and vascular malformations.

Microvascular anatomy of the cerebellar parafloccular perforating space

OBJECT

The cerebellopontine angle is a common site for tumor growth and vascular pathologies requiring surgical manipulations that jeopardize cranial nerve integrity and cerebellar and brainstem perfusion. To date, a detailed study of vessels perforating the cisternal surface of the middle cerebellar peduncle—namely, the paraflocculus or parafloccular perforating space—has yet to be published. In this report, the perforating vessels of the anterior inferior cerebellar artery (AICA) in the parafloccular space, or on the cisternal surface of the middle cerebellar peduncle, are described to elucidate their relevance pertaining to microsurgery and the different pathologies that occur at the cerebellopontine angle.

METHODS

Fourteen cadaveric cerebellopontine cisterns (CPCs) were studied. Anatomical dissections and analysis of the perforating arteries of the AICA and posterior inferior cerebellar artery at the parafloccular space were recorded using direct visualization by surgical microscope, optical histology, and scanning electron microscope. A comprehensive review of the English-language and Spanish-language literature was also performed, and findings related to anatomy, histology, physiology, neurology, neuroradiology, microsurgery, and endovascular surgery pertaining to the cerebellar flocculus or parafloccular spaces are summarized.

RESULTS

A total of 298 perforating arteries were found in the dissected specimens, with a minimum of 15 to a maximum of 26 vessels per parafloccular perforating space. The average outer diameter of the cisternal portion of the perforating arteries was 0.11 ± 0.042 mm (mean ± SD) and the average length was 2.84 ± 1.2 mm. Detailed schematics and the surgical anatomy of the perforating vessels at the CPC and their clinical relevance are reported.

CONCLUSIONS

The parafloccular space is a key entry point for many perforating vessels toward the middle cerebellar peduncle and lateral brainstem, and it must be respected and protected during surgical approaches to the cerebellopontine angle.

3D Computer graphics simulation to obtain optimal surgical exposure during microvascular decompression of the glossopharyngeal nerve

The affected artery in glossopharyngeal neuralgia (GPN) is most often the posterior inferior cerebellar artery (PICA) from the caudal side or the anterior inferior cerebellar artery (AICA) from the rostral side. This technical report describes two representative cases of GPN, one with PICA as the affected artery and the other with AICA, and demonstrates the optimal approach for each affected artery. We used 3D computer graphics (3D CG) simulation to consider the ideal transposition of the affected artery in any position and approach. Subsequently, we performed microvascular decompression (MVD) surgery based on this simulation. For PICA, we used the transcondylar fossa approach in the lateral recumbent position, very close to the prone position, with the patient's head tilted anteriorly for caudal transposition of PICA. In contrast, for AICA, we adopted a lateral suboccipital approach with opening of the lateral cerebellomedullary fissure, to visualize better the root entry zone of the glossopharyngeal nerve and to obtain a wide working space in the cerebellomedullary cistern, for rostral transposition of AICA. Both procedures were performed successfully. The best surgical approach for MVD in patients with GPN is contingent on the affected artery--PICA or AICA. 3D CG simulation provides tailored approach for MVD of the glossopharyngeal nerve, thereby ensuring optimal surgical exposure.

Distal aneurysm of the rostral duplicate anterior inferior cerebellar artery feeding an associated dural arteriovenous malformation: case report and review of the literature

A rare case of a distal aneurysm of a rostral, duplicate anterior inferior cerebellar artery feeding an associated dural arteriovenous malformation is reported. The patient presented with severe nuchal rigidity after sexual intercourse; no neurological deficit was seen. The aneurysm causing the subarachnoid hemorrhage was wrapped but the arteriovenous malformation was inoperable. An analysis of the literature showed 51 cases of coexisting aneurysms and arteriovenous malformations in the posterior fossa; only three of them had a dural arteriovenous malformation. A 7:3 male predominance was recognized. The mean age at diagnosis was 48.5 years. Ninety-four per cent presented with hemorrhage and 6% with cranial nerve deficit only. The bleeding originated from the aneurysm in 73% and from the arteriovenous malformation in 15%; in 12% the origin of bleeding was not mentioned or could not be identified. Outcome was satisfactory in 76%, poor in 7% and 17% died. Treatment of both lesions should be performed in a one-stage operation if technically feasible. Additionally, radiosurgery to surgically unresectable arteriovenous malformations should be considered in cases where aneurysms are clipped or coiled.

Aneurysm of the Anterior Inferior Cerebellar Artery-Posterior Inferior Cerebellar Artery Variant: Case Report with Anatomical Description in the Cadaver

OBJECTIVE AND IMPORTANCE

The authors report a very rare case of an aneurysm at the distal segment of the anterior inferior cerebellar artery-posterior inferior cerebellar artery (AICA-PICA) variant along with a description of the surgical anatomy of this variation in a cadaveric specimen.

CLINICAL PRESENTATION

A 44-year-old woman experienced the sudden onset of severe headache and vomiting. Computed tomographic scanning revealed subarachnoid and intraventricular hemorrhage. Cerebral angiography demonstrated a saccular aneurysm arising from the tonsillomedullary segment of the right PICA and a second aneurysm arising from the cortical segment of the common trunk of an AICA-PICA variation.

INTERVENTION

Via bilateral suboccipital craniotomy, both aneurysms were clipped.

CONCLUSION

Only two cases of aneurysms arising from an AICA-PICA variation have been reported in the literature and no detailed description of the surgical anatomy of this variation has been carried out in previous publications. To our knowledge, the present report is the first description of a clinical case along with a detailed surgical anatomic study in a cadaver.

Distal anterior inferior cerebellar artery aneurysm masquerading as a cerebellopontine angle tumor: case report and review of literature

We present the case of a distal anterior inferior cerebellar artery (AICA) aneurysm masquerading as a cerebellopontine angle tumor in a 60-year-old right-handed man with previously undiagnosed polyarteritis nodosa (PAN). The patient presented with a 2-month history of progressive right-sided hearing loss, intermittent severe headache, and sudden onset of complete facial paralysis 3 weeks before admission. Magnetic resonance imaging, including post-gadolinium images, showed a 1.2-cm heterogeneously enhancing mass that slightly enlarged the right internal auditory canal. A right suboccipital craniotomy was performed, and a partially thrombosed fusiform AICA aneurysm was discovered just anterior to the VII/VIII nerve complex. The aneurysm was trapped and opened, and a thrombectomy was performed. Postoperatively, the patient experienced abdominal pain; liver function tests were abnormal. Investigation revealed a small retroperitoneal hemorrhage and aneurysms of the celiac axis and gastroduodenal arteries. Further investigation revealed an increased erythrocyte sedimentation rate, and a diagnosis of PAN was made. PAN is a well-identified factor in the genesis of peripheral vascular aneurysms. Aneurysms involving the hepatic, renal, coronary, pancreatic, and tibial arteries have been described. PAN is an extremely rare cause of intracranial aneurysm. Patients who present with aneurysms in unusual locations (e.g., distal AICA) should be investigated for vasculopathy and collagen vascular disorders.

An anatomic variant of the anterior inferior cerebellar artery in a patient with Ménière's disease

OBJECTIVE

To describe an anatomic variant of the anterior inferior cerebellar artery in a patient with Ménière's disease.

STUDY DESIGN

Retrospective case review and review of the literature.

SETTING

Tertiary referral clinic.

INTERVENTION

Vestibular nerve section and microvascular decompression.

MAIN OUTCOME MEASURES

Audiometric testing and control of vertigo.

RESULTS

The eighth nerve was identified via a retromastoid approach. The anterior inferior cerebellar artery was observed bisecting the eighth nerve. The vestibular nerve was sectioned, and microvascular decompression was performed on the cochlear division. At last follow-up, the patient had not experienced any vertiginous attacks but was observed to have progressive hearing loss.

CONCLUSIONS

The course of the anterior inferior cerebellar artery is highly variable and difficult to predict. Knowing the potential paths is a necessity in performing posterior fossa surgery. Although the patient's vertigo was controlled by the vestibular nerve section, microvascular decompression of the cochlear nerve did not result in hearing improvement or stabilization. This case report does not support a benefit of microvascular decompression in Méniére's disease. Vestibular nerve section remains the authors' treatment of choice for controlling disabling vertigo caused by Ménière's disease.

Detailed magnetic resonance imaging anatomy of the cisternal segment of the abducent nerve: Dorello's canal and neurovascular relationships and landmarks

OBJECT

The goal of this study was to identify reliably the cisternal segment of the abducent nerve by using the three-dimensional Fourier transform constructive interference in steady-state (3-D CISS) magnetic resonance (MR) imaging sequence to define landmarks that assist in the identification of the abducent nerve on MR imaging and to describe the nerve's relationship to the anterior inferior cerebellar artery (AICA).

METHODS

A total of 26 volunteers underwent 3-D CISS MR imaging, and 10 of these volunteers also underwent MR angiography in which a time-of-flight sequence was used to identify the facial colliculus, the abducent nerve and its apparent origin, Dorello's canal, and the AICA. The authors identified the abducent nerve with certainty in 96% of 3-D CISS sequences obtained in the axial and sagittal planes and in 94% obtained in the coronal plane. The nerve emerged from the pontomedullary sulcus in 94% of cases. The facial colliculus could always be identified, and Dorello's canal was identified in 94% of cases. In 76.6% of cases, the abducent nerve was seen to contact the AICA, which passed inferior to the nerve in 63.8% of cases and superior to it in 29.8%.

CONCLUSIONS

The anatomical course of the abducent nerve and its relationship to the AICA and other blood vessels can be reliably identified using a 3-D CISS MR sequence with the facial colliculus and Dorello's canal serving as landmarks.

Posterior circulation infarction: anatomy, pathophysiology, and clinical correlation

Posterior circulation cerebrovascular disease may be responsible for clinical syndromes that are determined by the vascular territory affected. An anatomic/topographic approach to the brain stem and cerebellum, relating the cross-sectional and functional anatomy to the vascular supply territories, is useful in the analysis of imaging studies of patients with posterior circulation cerebrovascular disease. Knowledge of the typical vascular distributions may be particularly useful for cases that do not show the classical clinical brain stem and cerebellar infarction syndromes. This approach may serve to improve our understanding of cerebrovascular disease in the posterior fossa.

Value of parasagittal magnetic resonance images in visualizing the vascular territories of the cerebellum

The outcomes of infarctions of the cerebellar arteries may range from self-limited neuro-ophthalmic symptoms to sudden death. Identification of the affected territory may assist in clinical management because the vascular syndromes, as well as vascular mechanisms of cerebellar infarcts, are different according to the involved cerebellar arteries. However, it is usually difficult to tell the exact vascular territories using only transaxial imagings. Magnetic resonance imaging is a good tool for obtaining parasagittal and coronal images of the cerebellum, which are better for showing the vascular territories. To illustrate this point we report a 61-year-old woman and bilateral cerebellar infarcts (right posterior inferior cerebellar artery and left superior cerebellar artery who had vertigo, vomiting, headache, intermittent vertical diplopia, and difficulty walking. The clinical value of parasagittal imaging of the cerebellum in this case is discussed.

A study of neurotransmitters in human inner ear. Preservation of human temporal bone and value of organ donation for inner ear research

Twenty-nine human temporal bones (TBs) from 3 different groups of patients were used to investigate an effective preservation method of the inner ear and to study the suitability of TBs from organ donors for human inner ear research. Inner ears were fixed by perilymphatic perfusion and immersion fixation. Choline acetyltransferase (ChAT) and gamma-aminobutyric acid (GABA) activities were detected either by an indirect immunostaining method or by the peroxidase-anti-peroxidase (PAP) technique. The results show that the cytoarchitecture of the sensory epithelia is excellently preserved in specimens fixed within 2 h after death. ChAT- and GABA-immunoreactivities were revealed in the efferent nerve endings and fibers of the cochlea. Morphological preservation of the sensory epithelia was also good in specimens fixed within 5 h after death. However, inner ear sensory epithelia of organ donors that had died from head trauma and were in the definite brain death state for at least 7 1/2 h were severely damaged and showed cellular debris due to autolysis, although they were fixed within 2 1/2 h after death. The mechanisms underlying this damage of the sensory epithelia are discussed.

A case of cerebellar infarction occurred with the 8th cranial nerve symptoms

A rare case, 32-year-old man, of cerebellar infarction with the occurrence of the 8th cranial nerve symptoms was reported. On the neuro-otological examination, hearing test and caloric test showed a severe hearing loss and no response on the right side, respectively, and the spontaneous horizontal nystagmus fixed to the left direction was observed. Magnetic resonance (MR) imaging showed the infarctions in the areas of anterior inferior cerebellar artery (AICA) and posterior inferior cerebellar artery (PICA) on the right side. On the 14th illness day, the 8th cranial nerve symptoms disappeared, and on the 12th illness day, right hearing level and caloric response were significantly improved. We suggested that such an early recovery of the subjective symptoms and neuro-otological findings may be attributable to the recanalized circulation disturbance or the development of collateral circulation.

Infarction in the territory of the anterior inferior cerebellar artery: report of five cases

The clinical and MRI features were correlated in five cases of infarction in the territory of the anterior inferior cerebellar artery. The lateral portion of the pons area was affected in four cases, the middle cerebellar peduncle in two, and the cerebellar hemisphere in three. The lesion was restricted to the cerebellar hemisphere in one patient. In no case did the clinical features conform to the classical description.

The anterior inferior cerebellar artery (AICA): clinical and radiological significance

It is well known that the anterior inferior cerebellar artery (AICA) is difficult to visualize radiologically. As the analysis of 50 clinical cases shows, although the main branches of the AICA at the level of the basilar artery can be analyzed angiographically, the peripheral course is only vaguely visible. We examined 26 brains (postmortem) after selective resin-injection and preparation under an operation-microscope. Our results: 1. There is a reciprocal relationship between the development of the AICA and the PICA. 2. We can draw no conclusions concerning the pattern of the AICA of one side to the pattern on the other side. 3. The size of the AICA at the level of the basilar artery gives an indirect indication of the peripheral course. 4. The AICA and the cranial nerves are in a constant relationship to each other. Consideration of these relationships can help in the interpretation of angiograms done before microsurgical operations in the area of the cerebello-pontine angle.

Variability of the surgical anatomy of the neurovascular complex of the cerebellopontine angle

The variability of the anatomic relationship of the anterior inferior cerebellar artery (AICA) to the facial (seventh) and vestibulocochlear (eighth) nerves was studied in 52 cerebellopontine angles (CPAs) from 26 adult cadavers. The AICA originated from the basilar artery (98.1%) or from the vertebral artery (1.9%) as a single (92.3% of CPAs) or duplicate (7.7%) artery. Each of the 52 CPAs had one or more arterial trunks that coursed in close proximity to the seventh and eighth cranial nerves and thus were said to be nerve-related. The nerve-related arterial trunks were divided into three segments based on their relationship to the nerves and meatus: the premeatal, meatal, and postmeatal segments. The nerve-related branches of the AICA gave rise to the internal auditory artery in 92.3% of the CPAs, the recurrent perforating artery in 78.8%, and the subarcuate artery in 30.8%. The importance of understanding the surgical anatomy of the neurovascular complex of the CPA when performing a vestibular neurectomy is reviewed.

Aneurysms of the peripheral portion of the anterior inferior cerebellar artery; report of two cases

Two cases of extremely rare aneurysms of peripheral portions of the AICA are reported with a review of the pertinent literature. According to reported surgical findings, nearly all of the aneurysms originated from arterial loops near the internal acoustic meatus. These aneurysms can therefore, cause the cerebellopontine angle syndrome, with or without subarachnoid hemorrhage.

A comparative anatomical CT study of the vascular and nervous structures of the cerebello-pontine angle

The arteries and veins of the cerebellopontine angle have been injected with a contrast medium permitting a precise anatomical reconnaissance of their topography and relations. These specimens have been explored by CT in order to define the opacified vessels and to differentiate them from the adjacent nervous tissue. Thus in CT it is possible to locate the cerebellar arteries, the petrous and medullo-pontine veins and the nerves of the cerebello-pontine angle. This study describes the normal appearance of the flocculus from the arteries and veins. Moreover it should contribute to the definition of the criteria of reliability of a CT diagnosis and its limits in the cerebello-pontine angle.