Functional connectivity abnormalities in Type I Chiari: associations with cognition and pain

There is initial evidence of microstructural abnormalities in the fibre-tract pathways of the cerebellum and cerebrum of individuals diagnosed with Type I Chiari malformation. However, it is unclear whether abnormal white matter architecture and macro-level morphological deviations that have been observed in Chiari translate to differences in functional connectivity. Furthermore, common symptoms of Chiari include pain and cognitive deficits, but the relationship between these symptoms and functional connectivity has not been explored in this population. Eighteen Type I Chiari patients and 18 age-, sex- and education-matched controls underwent resting-state functional MRI to measure functional connectivity. Participants also completed a neuropsychological battery and completed self-report measures of chronic pain. Group differences in functional connectivity were identified. Subsequently, pathways of significant difference were re-analyzed after controlling for the effects of attention performance and self-reported chronic pain. Chiari patients exhibited functional hypoconnectivity between areas of the cerebellum and cerebrum. Controlling for attention eliminated all deficits with the exception of that from the posterior cerebellar pathway. Similarly, controlling for pain also eliminated deficits except for those from the posterior cerebellar pathway and vermis VII. Patterns of Chiari hyperconnectivity were also found between regions of the cerebellum and cerebrum in Chiari patients. Hyperconnectivity in all regions was eliminated after controlling for attention except between left lobule VIII and the left postcentral gyrus and between vermis IX and the precuneus. Similarly, hyperconnectivity was eliminated after controlling for pain except between the default mode network and globus pallidus, left lobule VIII and the left postcentral gyrus, and Vermis IX and the precuneus. Evidence of both hyper- and hypoconnectivity were identified in Chiari, which is posited to support the hypothesis that the effect of increased pain in Chiari draws on neural resources, requiring an upregulation in inhibitory control mechanisms and resulting in cognitive dysfunction. Areas of hypoconnectivity in Chiari patients also suggest disruption in functional pathways, and potential mechanisms are discussed.

Haematoma evacuation in cerebellar intracerebral haemorrhage: systematic review

BACKGROUND

Guidelines regarding recommendations for surgical treatment of spontaneous cerebellar intracerebral haemorrhage (ICH) differ. We aimed to systematically review the literature to assess treatment strategies and outcomes.

METHODS

We searched PubMed and Embase between 1970 and 2019 for randomised or otherwise controlled studies and observational cohort studies. We included studies according to predefined selection criteria and assessed their quality according to the Newcastle-Ottawa Scale (NOS) and risk of bias according to a predefined scale. We assessed case fatality and functional outcome in patients treated conservatively or with haematoma evacuation. Favourable functional outcome was defined as a modified Rankin Scale score of 0-2 or a Glasgow Outcome Scale score of 4-5.

RESULTS

We included 41 observational cohort studies describing 2062 patients (40% female) with spontaneous cerebellar ICH. A total of 1171 patients (57%) underwent haematoma evacuation. Ten studies described a cohort of surgically treated patients (n=533) and 31 cohorts with both surgically and conservatively treated patients (n=638 and n=891, respectively). There were no randomised clinical trials nor studies comparing outcome between the groups after adjustment for differences in baseline characteristics. The median NOS score (IQR) was 5 (4-6) out of 8 points and the bias score was 2 (1-3) out of 8, indicative of high risk of bias. Case fatality at discharge was 21% (95% CI 17% to 25%) after conservative treatment and 24% (95% CI 19% to 29%) after haematoma evacuation. At ≥6 months after conservative treatment, case fatality was 30% (95% CI 25% to 30%) and favourable functional outcome was 45% (95% CI 40% to 50%) and after haematoma evacuation, case fatality was 34% (95% CI 30% to 38%) and 42% (95% CI 37% to 47%).

CONCLUSIONS

Controlled studies on the effect of neurosurgical treatment in patients with spontaneous cerebellar ICH are lacking, and the risk of bias in published series is high. Due to substantial differences in patient characteristics between conservatively and surgically treated patients, and high variability in treatment indications, a meaningful comparison in outcomes could not be made. There is no good published evidence to support treatment recommendations and controlled, preferably randomised studies are warranted in order to formulate evidence-based treatment guidelines for patients with cerebellar ICH.

Diagnosis and management of progressive ataxia in adults

Progressive ataxia in adults can be difficult to diagnose, owing to its heterogeneity and the rarity of individual causes. Many patients remain undiagnosed (‘idiopathic’ ataxia). This paper provides suggested diagnostic pathways for the general neurologist, based on Ataxia UK’s guidelines for professionals. MR brain scanning can provide diagnostic clues, as well as identify ‘structural’ causes such as tumours and multiple sclerosis. Advances in molecular genetics, including the wider and cheaper availability of ‘next-generation sequencing’, have enabled clinicians to identify many more cases with a genetic cause. Finally, autoimmunity is probably an under-recognised cause of progressive ataxia: as well as patients with antigliadin antibodies there are smaller numbers with various antibodies, including some associated with cancer. There are a few treatable ataxias, but also symptomatic treatments to help people with the spectrum of complications that might accompany progressive ataxias. Multidisciplinary team involvement and allied health professionals’ input are critical to excellent patient care, including in the palliative phase. We can no longer justify a nihilistic approach to the management of ataxia.

Can patients with cerebellar disease switch learning mechanisms to reduce their adaptation deficits?

Systematic perturbations in motor adaptation tasks are primarily countered by learning from sensory-prediction errors, with secondary contributions from other learning processes. Despite the availability of these additional processes, particularly the use of explicit re-aiming to counteract observed target errors, patients with cerebellar degeneration are surprisingly unable to compensate for their sensory-prediction error deficits by spontaneously switching to another learning mechanism. We hypothesized that if the nature of the task was changed-by allowing vision of the hand, which eliminates sensory-prediction errors-patients could be induced to preferentially adopt aiming strategies to solve visuomotor rotations. To test this, we first developed a novel visuomotor rotation paradigm that provides participants with vision of their hand in addition to the cursor, effectively setting the sensory-prediction error signal to zero. We demonstrated in younger healthy control subjects that this promotes a switch to strategic re-aiming based on target errors. We then showed that with vision of the hand, patients with cerebellar degeneration could also switch to an aiming strategy in response to visuomotor rotations, performing similarly to age-matched participants (older controls). Moreover, patients could retrieve their learned aiming solution after vision of the hand was removed (although they could not improve beyond what they retrieved), and retain it for at least 1 year. Both patients and older controls, however, exhibited impaired overall adaptation performance compared to younger healthy controls (age 18-33 years), likely due to age-related reductions in spatial and working memory. Patients also failed to generalize, i.e. they were unable to adopt analogous aiming strategies in response to novel rotations. Hence, there appears to be an inescapable obligatory dependence on sensory-prediction error-based learning-even when this system is impaired in patients with cerebellar disease. The persistence of sensory-prediction error-based learning effectively suppresses a switch to target error-based learning, which perhaps explains the unexpectedly poor performance by patients with cerebellar degeneration in visuomotor adaptation tasks.

Pathogenesis of dystonia: is it of cerebellar or basal ganglia origin?

Dystonia is a disorder of motor programmes controlling semiautomatic movements or postures, with clinical features such as sensory trick, which suggests sensorimotor mismatch as the basis. Dystonia was originally classified as a basal ganglia disease. It is now regarded as a 'network' disorder including the cerebellum, but the exact pathogenesis being unknown. Rare autopsy studies have found pathology both in the striatum and the cerebellum, and functional disorganisation was reported in the somatosensory cortex in patients. Recent animal studies showed physiologically tight disynaptic connections between the cerebellum and the striatum. We review clinical evidence in light of this new functional interaction between the cerebellum and basal ganglia, and put forward a hypothesis that dystonia is a basal ganglia disorder that can be induced by aberrant afferent inputs from the cerebellum.