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Gross (Mesoscopic) and Applied Anatomy of the Anterior Inferior Cerebellar Artery in Man with Special Reference to Its Course through the Cerebellopontine Angle Region
Abstract
In the present paper, we describe anatomical variants of the anterior inferior cerebellar artery in man for applicative purposes. Our goal was to provide the surgeon with a detailed anatomical view of the region. This is similar to what he may observe through the surgical microscope using modern microsurgical techniques. We have focused our attention on the segments of the artery comprising its origin, its course until it reaches the cerebellum and its main collateral branches. Our results confirm the great variability of the elements under study, but enable the establishment of a few basic variational patterns. These patterns together with their relative frequency may be helpful in microsurgery.
... Variation in the caliber of the vessel depends largely upon the size and distribution of the posterior inferior cerebellar artery (PICA). Stopford and Atkinson have also observed that variation in size of the AICA usually is in inverse proportion to the size of the PICA [3,9,21] (Fig. 2a, b). ...
... The cerebellopontine angle is surgically an important region, due to high frequency of vascular and neural lesions that are located in the vicinity of the internal acoustic meatus [9]. The vessels in the region of the cerebellopontine angle are surgically important as they supply the VIIth and VIIIth cranial nerves, the bony labyrinth and other cerebellar and brainstem structures and injury to them may cause facial paralysis, hearing loss, brainstem and cerebellar lesions. ...
... The vessels in the region of the cerebellopontine angle are surgically important as they supply the VIIth and VIIIth cranial nerves, the bony labyrinth and other cerebellar and brainstem structures and injury to them may cause facial paralysis, hearing loss, brainstem and cerebellar lesions. Additionally, tumors located in the CPA can cause variable displacements, especially of the AICA [9,22,27]. ...
Cerebellopontine angle and vascular supply of adjacent brainstem and cerebellum are susceptible to compression and eventual damage by tumors. Delicate and complicated neurosurgical operations in the cerebellopontine angles of the brainstem, where lateral recesses of fourth ventricle empty, are abundant especially operations in which foramina of Luschka are used as possible access to the floor of the fourth ventricle. So awareness and knowledge of the normal anatomical features of the region is valuable for neurosurgeons. Arteries of 40 human cerebella were injected with colored gelatin to investigate the microsurgical anatomy around the foramen of Luschka in the cerebellopontine angle. Two compartments of the foramen of Luschka were distinguished, choroidal part and the patent part. Seventy-four (92.5%) of foramina were open and only 6 (7.5%) foramina were closed. The mean distance between the foramen of Luschka and the anterior inferior cerebellar artery was 3.90 mm on the left side and 3.89 on the right side. The distance from the posterior inferior cerebellar artery was 7.08 and 5.81 mm to the left and right foramina of Luschka, respectively. In ten cases, tortuous vertebral artery was occupying the left cerebellopontine angle space and the foramen of Luschka.
... Similar findings have been described by authors such as Haidara et al., in 2013, who reported the prevalence of LA originating from AICA to be 90 % and from BA 10 % [12]. Other examples of analogous results include studies by Jiménez-Castellanos et al. from 1992, who described 96 % of LAs starting from AICA or by Dos Santos et al. from 2020, who reported the prevalence of LA originating from AICA to be 96,6 % and from BA only 3,4 % [13,14]. Moreover, Kim et al., in 1990 observed an even higher prevalence of AICA origin which ranged up to 98 % [15]. ...
... Presence of more than 1 LA was also depicted by Brunsteins et al., in 1990 with 38,5 % of cases with monoarterial and 61, 5 % biarterial systems, whereas Ishii et al., in 1964 in their observations of 20 Japanese described 7 biarterial LAs (17,5 %)[29,30]. Jiménez-Castellanos et al. found miscellaneous variants of LA numbers, as 43,3 % were monoarterial, 46,6 % biarterial and what is more, there were 10 % of triple LAs[13]. Similar outcomes were described byMazzoni et al., in 1969 -in 51 % cases LA was single, in 45 % double ...
Abstract:
The labyrinthine artery (LA), is a major vessel responsible for blood supply of labyrinth and
cochlea in the inner ear, as well as cranial nerves, including vestibulocochlear and facial
nerves. Its origin varies throughout numerous reports, however the most commonly reported
origins include anterior inferior cerebellar artery (AICA) and basilar artery (BA).
Nevertheless, arteries such as superior cerebellar, vertebral and posterior inferior cerebellar
artery have also been reported as the sources of LA. What is more, the relationship between
LA and vestibulocochlear and facial nerves has been described vaguely in many publications.
The aforementioned not only represent anatomical idiosyncrasies, but the area of LA origin is
also crucial from a clinical perspective, especially when performing a wide spectrum of skull
base approaches, most commonly involving exposure of cerebellopontine angle. The
thorough knowledge regarding LA course, branches, correlation with cranial nerves can be
critical in prevention of iatrogenic lesions, which may occur during various approaches such
as middle cranial fossa, rectosigmoid and labyrinthine (both trans- and retro) ones.. Lastly,
we should remember that many different variants of LA can lead to a broader range of
symptoms in the case of vascular changes, such as aneurysms.
This publication's aim is to provide a brief overview on all possible variants of labyrinthine
arteries described in the literature, as well as its trajectories in relation to vestibulocochlear
and facial nerves.
The anatomical complexity of the vascularization of the posterior cranial fossa finds its greatest expression in the variations in number, origin, morphology and course of the anterior inferior cerebellar artery (AICA).
Introduction:
Protrusions of fourth ventricular choroid plexus through the foramina of Luschka are called 'Bochdalek's flower basket' (BochFB). The bulbous terminal expansions (cornucopiae) extend into the cerebellopontine angle (CPA) cisterns. We studied and reviewed the normal imaging anatomy, morphometry and anatomical variants of BochFB.
Methods:
We retrospectively analysed normal brain imaging findings on axial pre- and post-contrast CT scans and enhanced axial T1-weighted MRIs of 200 patients. We assessed BochFB for: (a) calcification, (b) lateral extension, (c) enhancement pattern, (d) cornucopiae shape, (e) symmetry and (f) proximity to tortuous vertebral arteries and morphometry of cornucopiae size and length of BochFB limbs.
Results:
BochFB calcification was found in 38 % of patients aged over 51 years. Lateral extension of BochFB into the CPA cistern was prominent in 75 % on CT and 96 % on MRI. The mean length of these extensions was 23.6 mm. BochFB enhanced strongly in 47 % on CT and 66 % on MRI. The BochFB cornucopiae were bulbous in 51 % on CT and 54 % on MRI. The mean width of bulbous cornucopiae was 3.5 mm. Bilateral BochFB symmetry was found in 71 % on CT and 80 % on MRI. Six to 8 % of tortuous left vertebral arteries were close to BochFB.
Conclusion:
The cornucopiae are particularly well demonstrated on post-contrast MRI. However several sources of error in image interpretation may arise when imaging the normal BochFB on routine head CT and MRI. Difficulties in analysis arise especially on CT because of physiologic calcification, asymmetry, and the bulbous cornucopiae being mistaken for aneurysms.
In the present paper we have studied the gross (mesoscopic) anatomy of the ophthalmic a. in humans, using magnification by microsurgical systems to obtain data on the origin and course of this artery and its main collateral branches. Comparison of our results with previous reports indicates that, although the anatomical variations of the vascular system are well known, some patterns of frequency may be emphasised. Thus, the ophthalmic a. was usually found as a collateral branch of the internal carotid a., although other origins were also found. The ophthalmic a., once inside the orbit, followed a course above the optic nerve in most cases. All the collateral branches of the ophthalmic a., with the exception of the muscular branches, showed great constancy.
A rabbit model was developed to simulate the effects of ischemia that may occur during surgical removal of tumors involving the cerebellopontine angle or internal auditory canal. Specifically, the internal auditory artery was visualized through a posterior craniotomy and mechanically compressed for repetitive 1-minute intervals with a micromanipulator-controlled glass pipet terminating in a smooth bead. The 2f1-f2 distortion-product otoacoustic emissions were used to monitor the susceptibility of cochlear function to compressive effects. Distortion-product otoacoustic emissions were measured during discrete preblock, block, and postblock periods to determine the time course of distortion-product otoacoustic emission reduction and its return to baseline levels after rapid obstruction and resumption, respectively, of the cochlear vascular supply. Comparisons during these times indicated that preblock distortion-product otoacoustic emission levels were very stable, often varying by less than 1 dB. Additionally, distortion-product otoacoustic emissions were very sensitive to brief vascular occlusions in that, within approximately 25 seconds of blockage onset, emission levels at all frequencies decreased at rates of about -1.5 dB/second. On alleviation of the occlusion, distortion-product otoacoustic emissions rapidly and completely returned to preblock levels with a delay of about 4 seconds and recovery slopes of about 10.5 dB/second. A notable finding in some animals was that early and reproducible variations in distortion-product otoacoustic emission levels occurred within 5 to 8 seconds of internal auditory artery compression. When present, these transitory changes in distortion-product otoacoustic emission levels acted as early warning signs for vascular compromise of cochlear function.
The introduction in the sixties of magnification tools in surgery has created the need for a precise anatomical knowledge of morphological structures that was previously unnecessary from a clinical perspective. In the present paper, we have centred our attention on the intracavernous portion of the internal carotid artery (arteria carotis interna) in humans for applicative purposes. With the aid of a surgical microscope and the corresponding microdissecting material we have analysed the branches emerging from this arterial segment. Our results are compared with previous data appearing in the literature, the latter sometimes confusing because of the different terminologies used to refer to these vessels. The elements under study varied greatly, but some basic variational parameters were deduced.
Changes in cochlear blood flow (CoBF) and auditory brainstem response (ABR) in a pressure-induced animal model of acoustic neuroma were examined. A suboccipital approach was used to expose the right cerebello-pontine angle in guinea pigs. Under surgical microscope, the bundle of nerves and vessels at the entrance of the internal auditory meatus was exposed without retraction. The two pressure points, one anterior to and the other posterior to the center of the bundle were separately compressed by a pressure probe (1mm in diameter). CoBF from the basal turn or second turn of the right cochlea was measured with a laser Doppler flowmeter. ABR was recorded from the electrodes placed on the vertex and the right mastoid process. With compression, the changes in CoBF and ABR were found in a total of 19 animals. We classified these changes into three types based mainly on CoBF. In type I (n = 9), an increase rather than a decrease of CoBF was noted, and an increase in the I-II inter-peak latency with a decrease in the amplitudes of wave II-IV in ABR were observed. Those changes were mainly attributed to the blockage of cochlear nerve. In type II (n = 6), CoBF was completely stopped and all waves of ABR disappeared during compression. This suggested the presence of cochlear ischemia. After relaxation of compression both CoBF and ABR recovered, but I-II inter-peak latency remained delayed. CoBF in type III (n = 4) decreased and then slowly recovered. In type III, all waves transiently disappeared, and wave I reappeared with recovery of CoBF. The changes in type III were caused by damage to both the artery and the nerve. In addition, the changes in CoBF and ABR were closely related to the pressure points. The changes in type I were often found in compression of the anterior pressure point, whereas the changes in type II are associated with the posterior pressuring point (p < 0.05). The results indicate that the cochlear nerve or the internal auditory artery is more susceptible to damage by compression of an anterior or posterior pressure point, and that the compression position is an important determinant in the type of auditory dysfunction and the degree of hearing loss.
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.
Anticoagulant therapy is effective and prevents death in more than 95% of patients with pulmonary embolism following deep vein thrombosis. We report a patient who developed deep vein thrombosis following rupture of a dissecting aneurysm of the internal auditory artery. The parent artery was occluded before anticoagulant therapy as a prophylactic measure to prevent intracranial haemorrhage. We discuss some of the clinical features, therapeutic difficulties, and pitfalls in the management of internal auditory artery aneurysm complicated by deep vein thrombosis.
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