Timothy C. Hain, MD • Page last modified: July 29, 2022-->
The AICAstroke syndrome usually consists of vertigo and unilateral ipsilateral deafness from labyrinthine artery ischemia. Large strokes are accompanied by ipsilateral facial weakness and ataxia. It is the second most common brainstem stroke, after PICA -- it is about 10% of PICA frequency.
AICA territory strokes are probably the most common brainstem strokes that cause of hearing loss. This is because the internal auditory artery( IAA) the principal artery for vascular supply to the inner ear, usually originates from the AICA (Mazzoni 1969; Hausler and Levine 2000; Mazzoni 1990). Lee and associates reported that out of 82 patients with AICA territory infarctions, 59.8% had “combined audiovestibular loss” (Lee et al. 2009). The more frequent PICA territory strokes, while also source of vertigo, are rarely accompanied by hearing loss.
The IAA supplies the cochlea and vestibular labyrinth, and occlusion of the IAA causes a loss of auditory and vestibular function, resulting in hearing loss and vertigo, and so-called labyrinthine (inner ear) infarction. Perhaps because the IAA is often duplicated, the site of lesion in an IAA infarction mostly occurs due to thrombotic narrowing of the AICA itself, or in the basilar artery at the orifice of the AICA(Mazzoni 1990; Amarenco et al. 1993). Pathological examination in patients with inner ear infarction show widespread necrosis of the cochlea and vestibular end organs (Hinojosa and Kohut 1990) .
When labyrinthine infarction occurs, infarction of the brainstem and/or cerebellum in the territory of the AICA is usually associated (Lee et al. 2002; Amarenco et al. 1993; Amarenco and Hauw 1990a; Hinojosa and Kohut 1990). Rarely occlusion of the AICA causes sudden deafness and vertigo without brainstem or cerebellar signs, or isolated auditory or vestibular loss, in which case the diagnosis may be made from a small infarct seen on brain MRI (Lee et al. 2009). In spite of this possibility, in general, almost all sudden hearing loss cases deemed idiopathic, rather than being attributed to stroke (Singh and Kumar Irugu 2020; Chau et al. 2010).
The extent of the AICA stroke isextremely variable. Symptoms similar to Meniere's disease (fluctuating hearing, tinnitus, vertigo) can also be caused by impending TIA's in this distribution (Lee and Cho, 2003). Bilaterality of hearing fluctuation suggests a vascular cause, but most AICA strokes present with unilateral hearing symptoms. The AICA also has a very variable origin and may take origin from the caudal to middle pons. AICA territory strokes may also present with vertigo alone.
Diagnosis is generally via MRI. The image above shows a pontine stroke attributed to an AICA infarct.