Guide
Dizziness, vertigo, and ataxia are common symptoms of posterior circulation ischemia, and cerebellar stroke is the most affected area of these symptoms. Cerebellar stroke is more likely to be misdiagnosed than stroke in the cerebral hemispheres, so it is important to understand the symptoms of infarction in different areas of the cerebellum. This article provides an overview of the characteristics of infarction in different parts of the cerebellum for your reference.
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Overview of cerebellar blood supply
The cerebellum is supplied by the posterior inferior artery (PICA), anterior inferior artery (AICA), and superior artery (SCA) (Figure 1). In central vascular vertigo syndrome, cerebellar stroke is the highest among all causes, and vertigo is the only symptom in about 11% of patients with isolated cerebellar infarction, most of whom are infarcted in the medial ramus of PICA.
Figure 1 Schematic diagram of cerebellar blood supply
10%~25% of patients with cerebellar infarction may have a mass effect, and the infarction in the PICA region is more likely to cause the mass effect than the infarction in the SCA region. Large cerebellar infarction can lead to compression of the brainstem, leading to hydrocephalus, cardiopulmonary complications, coma, and death. Therefore, correct recognition of cerebellar stroke is important for subsequent treatment, especially in the acute phase.
Infarction of the posterior inferior artery supply area of the cerebellum
PICA is the main blood supply to the cerebellum. Because vestibulocerebellar structures, such as cerebellar nodules and vermilobes, are supplied to PICA, patients with cerebral infarction in the PICA-supplied area are often accompanied by dizziness and imbalance. Patients often do not have significant cerebellar signs, such as dysarthria, and limb paralysis, and a detailed neurologic evaluation is required in these patients, particularly those with medial branch infarction of PICA.
In fact, approximately 17% of patients with PICA infarction have symptoms that mimic those of acute peripheral vestibular lesions. One study included 72 patients with cerebellar infarction, most of whom had PICA, and 39% of these patients developed spontaneous nystagmus. Although severe imbalance (71 percent) and gaze-induced nystagmus with variable orientation (54 percent) were also present, the sensitivity and specificity of these signs and symptoms were suboptimal, and only about half of patients showed signs of central vestibular dysfunction.
In contrast, in order to better identify the cause of acute spontaneous vertigo syndrome, the head pulse test (HIT) is useful in differentiating cerebellar infarction from inner ear disease in the PICA-supplied area. Bedside HIT findings have always been negative in patients with isolated vertigo due to PICA. In addition, the structures involved in unidirectional gaze-induced nystagmus include the vermicom, vermilobe, cerebellar tonsils and other parts, and the presence of gaze-induced nystagmus may also be a sign of damage to the midline and subcerebellar structures.
The role of vestibular evoked myogenic potentials (VEMPs) in the diagnosis of cerebellar infarction has been controversial. The HINTS test, which includes a cephalic pulse test (head shake test), nystagmus, and a crossed ocular occlusion test, can help distinguish central causes from peripheral causes. For more information about the HINTS examination, please refer to: "Teach you how to examine patients with dizziness and vertigo".
Infarction of the anterior inferior cerebellar artery supply
AICA supplies blood to peripheral and central vestibular structures, including the inner ear, lateral pons, cerebellar mid-foot, and other sites. As a result, AICA infarction usually results in peripheral and central vestibular lesions. Patients with infarction in the AICA supply area present with a combination of various symptoms such as dizziness/vertigo, nystagmus, hearing loss, loss of limb and facial sensation, ataxia, and dysmetria. When the pons bulbar is involved, AICA stroke can present with ipsilateral upper and lower facial weakness.
Although less common than PICA infarction, AICA infarction can cause sudden vertigo and ipsilateral sensorineural hearing loss, which results from vestibulocochochlear nerve and inner ear ischemia supplied by the labyrinthine artery. Hearing loss detected during the acute phase of infarction usually resolves over time. Inner ear dysfunction may precede infarction of AICA-supplied cerebellar tissue, possibly due to the relatively more fragile tolerance of ischemia by the vestibular structures of the inner ear or brainstem.
According to the neurological manifestations, some scholars have proposed 8 subtypes of AICA infarction, among which auditory and vestibular loss are the most common. However, the diagnosis of infarction in the AICA supply area remains a challenge, especially when symptoms and signs other than inner ear infarction are absent or not apparent.
It is important to note that the HINTS test, although one of the most useful tests for the detection of central vestibular lesions, may not be as powerful as the test results for AICA infarction. Studies have shown that in 5 out of 18 patients with AICA infarction, central lesions were not detected by HINTS testing. Therefore, in order to further improve the accuracy of diagnosis, other tests, such as shaking head to induce nystagmus, may be required.
Infarction of the superior cerebellar artery supplying area
Because SCA supplies blood to the caudal midbrain and posterior cerebellum, infarctions in the SCA supply area can be observed with ipsilateral trochlear nerve palsy, Horner syndrome, and contralateral ataxia. However, in SCA infarction, midbrain involvement is rare, and patients with SCA infarction rarely have the typical presentation of trochlear nerve palsy + Horner syndrome + ataxia at the same time.
Cerebellar infarction in the SCA-supplied area rarely causes vertigo because the upper cerebellum supplied by the SCA does not have structures significantly associated with the vestibule. However, in a recent study, vertigo and nystagmus in SCA infarction were more common than previously thought in about half of patients with isolated SCA infarction, and that 27% of patients had spontaneous or staring-induced nystagmus.
Unilateral medial branch infarction of SCA can cause saccades that are excessive to the contralateral and ipsilateral saccades, and can cause ipsilateral limb distoria. Patients with infarction involving the supracerebellar foot alone present with ocular torsion, mild dysarthria, and ipsilateral limb ataxia, but no abnormal saccades.
brief summary
The characteristics of infarction in each cerebellar supply area are summarized in the following table.
Bibliography:
[1] Choi K D, Lee H, Kim J S. Ischemic syndromes causing dizziness and vertigo[J]. Handbook of Clinical Neurology, 2016, 137:317.
[2] Southerland A M. Clinical Evaluation of the Patient With Acute Stroke[J]. Continuum Lifelong Learning in Neurology, 2017, 23(1):40-61.