The cerebellum is a complex and multifunctional structure that is essential for a wide range of motor and cognitive functions. Moreover, the cerebellum is also engaged in a variety of processes, such as the processing of sensory data, the control of eye movements, the control of balance and posture, and the coordination of motions (1). In terms of memory formation, the cerebellum is involved in the acquisition and retention of motor skills through long-term changes in synaptic connections which result in the formation of motor memory (2, 3).

A cerebellar stroke is a type of cerebrovascular event involving the posterior cranial fossa. Arterial obstruction leads to impaired blood and oxygen delivery following impaired perfusion which leads to deficits in motor and balance control (4). However, presenting symptoms are often non-specific and overlap with other neurologic, cardiovascular, gastrointestinal, and systemic conditions which often makes rapid diagnosis difficult (5). Surgical decompressive suboccipital craniotomy/craniectomy with or without removal of the infarcted tissue is indicated in cases with a space-occupying cerebellar infarction to prevent coma and death. Well-established risk factors for the development of cerebellar stroke include vasculopathies such as atherosclerosis or arterial dissections, specifically of the vertebral arteries (6). Data on functional outcomes after cerebellar stroke are sparse, and the reasons for poor outcomes remain unclear (7–9). Among the discussed causes is the strength-sapping rehabilitation process that is dependent on a vigorous nutritional condition (10).

However, the current topic of great interest in the scientific community is frailty. Frailty defines a state of increased vulnerability, decreased physiological reserves, and reduced capacity to withstand stressors. It is often associated with aging and can result from a combination of factors such as chronic diseases, functional decline, cognitive impairment, and nutritional deficiencies. Frail individuals are at a higher risk of adverse health outcomes, including falls, hospitalization, disability, and mortality due to their decreased ability to recover from illness or other challenges.

On the other hand, the radiological measurement of skeletal muscle mass was recently introduced as an objective parameter for outcomes in brain tumor, subdural hematoma, and stroke patients (11–13). Cranial computed tomography (CT) scans and magnetic resonance imaging (MRI) are routinely performed on cerebellar stroke patients; therefore, temporal muscle thickness (TMT) measurement is easy to perform and quick to implement. We investigated TMT as a parameter to evaluate patient frailty and investigated its role as a novel prognostic marker for cerebellar stroke outcomes.

This study investigates the role of TMT on conventional cranial CT and MRI scans performed on patients with cerebellar ischemic stroke. The major finding is the significant association between low TMT and decreased admission, as well as discharge and 12-month follow-up status. The findings of this study suggest that TMT may represent an objective parameter with prognostic value, which is novel for cerebellar ischemic stroke patients.

Frailty and the often synonymously used term of sarcopenia are becoming increasingly important in the scientific community due to their reliable prognostic value in brain tumor patients and increasingly extended to other neurosurgical conditions such as neurotrauma (14, 15). For instance, Namgung et al. recently showed the association between temporal muscle mass and early cognitive function in patients with mostly supratentorial acute ischemic stroke. The analysis showed that TMT was an independent predictor of early post-stroke cognitive function, stratified by the MoCA score (16).

However, an objective measurement of sarcopenia in clinical practice is hampered as it is usually verified through muscle function tests such as the gait speed test and/or the grip strength test, which often cannot be performed in ischemic stroke patients due to frequently present disturbances of consciousness and/or neurologic deficits (13, 17, 18). Another fact is that clinical deficits after isolated cerebellar stroke are subtle and poorly represented by the NIHSS, and the demand for alternative predictive parameters in this cohort is therefore crucial (19).

In our cohort, patient age was significantly associated with reduced TMT both in the univariate and multivariate analyses. We considered the possibility of bias with respect to the fact that older patients are intrinsically at higher risk for poor clinical outcomes and that this fact could undermine the role of TMT. However, even if accounting for the fact that muscle mass could be affected by age, sarcopenia as such is affected by several additional age-unrelated factors such as hormonal changes or inflammation. Furthermore, in contrast to the classical predictors of outcome in supratentorial stroke, several studies reported no association between patient age and clinical outcome (4, 6). Furthermore, other studies could not show a significant association between patients' age and TMT (Katsuki et al.). In summary, we value the age-related correlation between TMTs but insist on the value of TMT as an independent risk factor for poor outcomes in ischemic stroke patients. However, for a detailed classification of the data presented here, TMT values should be measured for a healthy comparison group in future prospective studies.

In terms of the analyzed preexisting comorbidities, only atrial fibrillation showed an association with reduced TMT, a finding that was statistically non-significant in the multivariate analysis. The role of comorbidities in the outcome after cerebellar stroke remains ambiguous, and several studies failed to observe a significant role of comorbidity in the prediction of functional outcomes after acute cerebellar infarctions (20). In our opinion, this fact undermines the significance of the TMT by largely excluding the preexisting conditions as bias.

With regard to the correlation between TMT and outcome in stroke patients, a recent analysis by Sakai et al. reported the association between reduced TMT and ischemic cerebral stroke-related dysphagia in 56 patients (21). However, these results are conflicting since TMT measurement using brain CT was not related to functional outcomes in older patients with acute cerebral stroke in the analysis of Nozoe et al. (10). Of note, patients with dysphagia were excluded from this study, which could contribute to the negative finding since recent reports suggested that sarcopenia is one of the causes of post-stroke dysphagia (22, 23). Unfortunately, our analysis of cerebellar stroke patients did not include the analysis of dysphagia, which certainly should be addressed in future.

Regarding the role of TMT after cerebral ischemic stroke, we report for the first time that TMT, after acute cerebellar stroke, is a disease compromising only 1.5% of all ischemic strokes (5). Our study adds an important input of the rare cohort of cerebellar ischemic strokes, which is not studied in the abovementioned analysis. Low TMT was significantly associated with reduced outcomes at discharge and at 12 months.

Since data on factors that influence recovery in patients with cerebellar ischemic stroke are rare, we propose the TMT assessment in cerebellar stroke as an objective parameter with prognostic value, novel for cerebellar stroke patients.

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.

The studies involving humans were approved by Ethics Committee of the University Medicine Rostock, Germany (Identification number: A 2021-0112). The studies were conducted in accordance with the local legislation and institutional requirements. Written informed consent for participation was not required from the participants or the participants' legal guardians/next of kin in accordance with the national legislation and institutional requirements.

DD and S-YW collected the data and wrote the first draft. FG supervised the manuscript. All authors supplied additional information, edited the manuscript, and contributed to the critical review and revision of the manuscript.