Cerebellar Vermis Relative Hypermetabolism: An Almost Constant PET Finding in an Injured Brain

Upper cerebellar glucose hypermetabolism in patients with temporal lobe epilepsy and interictal psychosis

OBJECTIVE

Psychosis is an important comorbidity in epilepsy, but its pathophysiology is still unknown. The imaging modality ¹⁸ F-fluorodeoxyglucose-positron emission tomography (¹⁸ F-FDG PET) is widely used to measure brain glucose metabolism, and we speculated that ¹⁸ F-FDG PET may detect characteristic alteration patterns in individuals with temporal lobe epilepsy (TLE) and psychosis.

METHODS

We enrolled 13 patients with TLE and interictal psychosis (TLE-P) and 21 patients with TLE without psychosis (TLE-N). All underwent interictal ¹⁸ F-FDG-PET scanning. Statistical Parametric Mapping (SPM)12 software was used for the normalization process, and we performed a voxel-wise comparison of the TLE-P and TLE-N groups.

RESULTS

Cerebral hypometabolic areas were observed in the ipsilateral temporal pole to hippocampus in both patient groups. In the TLE-P group, the voxel-wise comparison revealed significantly increased ¹⁸ F-FDG signals in the upper cerebellum, superior cerebellar peduncle, and midbrain. There were no significant between-group metabolic differences around the focus or other cerebral areas.

SIGNIFICANCE

Our results demonstrated significant hypermetabolism around the upper cerebellum in patients with TLE and interictal psychosis compared to patients with TLE without psychosis. These findings may reflect the involvement of the cerebellum in the underlying neurobiology of interictal psychosis and could contribute to a better understanding of this disorder.

Autoimmune cerebellar hypermetabolism: Report of three cases and literature overview

We report three cases of vermian cerebellar hypermetabolism in patients with autoimmune encephalitis. One of our patients was positive for anti-Ma2 antibodies and one for anti-Zic4 antibodies while the remaining patient did not present any known antibodies. The seronegative patient deteriorated after immune checkpoint inhibitor treatment for a pulmonary adenocarcinoma and improved with immunosuppressive drugs, which is in favour of an underlying autoimmune mechanism. They all presented with subacute neurological symptoms. Brain magnetic resonance imaging was normal except in one patient, where hyperintensities were present on FLAIR sequence around the third ventricle and the cerebral aqueduct. ¹⁸F-FDG brain positron emission tomography with computed tomography (¹⁸F-FDG PET-CT) demonstrated an unusual vermian cerebellar hypermetabolism in the three cases. While cerebellar hypermetabolism on ¹⁸F-FDG PET-CT has been described in various neurological diseases, such vermian - and more broadly cerebellar - hypermetabolism was seldom described in previous studies on autoimmune encephalitis. When differential diagnoses have been ruled out, this pattern may be of interest for the positive diagnosis of autoimmune encephalitis in difficult diagnostic cases.

PET and Single-Photon Emission Computed Tomography in Brain Concussion

This article offers an overview of the application of PET and single photon emission computed tomography brain imaging to concussion, a type of mild traumatic brain injury and traumatic brain injury, in general. The article reviews the application of these neuronuclear imaging modalities in cross-sectional and longitudinal studies. Additionally, this article frames the current literature with an overview of the basic physics and radiation exposure risks of each modality.

Altered Cerebellar White Matter Integrity in Patients with Mild Traumatic Brain Injury in the Acute Stage

Background and Purpose

Imaging studies of traumatic brain injury demonstrate that the cerebellum is often affected. We aim to examine fractional anisotropy alteration in acute-phase mild traumatic brain injury patients in cerebellum-related white matter tracts.

Materials and Methods

This prospective study included 47 mild traumatic brain injury patients in the acute stage and 37 controls. MR imaging and neurocognitive tests were performed in patients within 7 days of injury. White matter integrity was examined by using diffusion tensor imaging. We used three approaches, tract-based spatial statistics, graphical-model-based multivariate analysis, and region-of-interest analysis, to detect altered cerebellar white matter integrity in mild traumatic brain injury patients.

Results

Results from three analysis methods were in accordance with each other, and suggested fractional anisotropy in the middle cerebellar peduncle and the pontine crossing tract was changed in the acute-phase mild traumatic brain injury patients, relative to controls (adjusted p-value < 0.05). Higher fractional anisotropy in the middle cerebellar peduncle was associated with worse performance in the fluid cognition composite (r = -0.289, p-value = 0.037).

Conclusion

Altered cerebellar fractional anisotropy in acute-phase mild traumatic brain injury patients is localized in specific regions and statistically associated with cognitive deficits detectable on neurocognitive testing.

PET Imaging for Traumatic Brain Injury

Traumatic brain injury represents a substantial public health problem for which clinicians have limited treatment avenues. Traditional FDG-positron emission tomography (PET) brain imaging has provided unique insights into this disease including prognostic information. With the advent and implementation of novel tracers as well as improvement in instrumentation, molecular brain imaging using PET can further illustrate traumatic brain injury pathophysiology and point to novel treatment strategies.

Hippocampal remodelling after MDMA neurotoxicity: a single case study

Acute ingestion of MDMA (ecstasy) causes a transient marked increase in serotonin and dopamine at central synapses. Recent studies demonstrated that MDMA induces damage of serotonergic nerve terminals and alters hippocampal processing. Pronounced cognitive deficits in MDMA users affect learning and memory abilities. This pattern of predominant and long-lasting memory dysfunction suggests that the functioning of the hippocampus might be affected by the neurotoxic effects of MDMA. We present the case of a 16-year-old girl who developed an acute organic and psychotic syndrome caused by occasional use of low to moderate dose of MDMA. Serial neuroimaging ((18)F-FDG-PET and brain MRI) were correlated with her neurocognitive performance and clinical evolution. The structural and metabolic changes correlated with a severe cognitive impairment. After 16 months of intensive neuropsychological rehabilitation she showed significant improvement in hippocampal-related memory cognitive functions, which correlated with normalization of her (18)F-FDG-PET and remarkable hippocampal remodelling. This case report indicates that even non-chronic MDMA use may cause subacute toxic encephalopathy in which the clinical evolution is paralleled by neuroimaging changes in specific cerebral areas. The most relevant aspect is the reversibility of the volumetric changes, which may be the structural correlate of an ongoing hippocampal remodelling.

A review of perioperative glucose control in the neurosurgical population

Significant fluctuations in serum glucose levels accompany the stress response of surgery or acute injury and may be associated with vascular or neurologic morbidity. Maintenance of euglycemia with intensive insulin therapy (IIT) continues to be investigated as a therapeutic intervention to decrease morbidity associated with derangements in glucose metabolism. Hypoglycemia is a common side effect of IIT with potential for significant morbidity, especially in the neurologically injured patient. Differences in cerebral versus systemic glucose metabolism, the time course of cerebral response to injury, and heterogeneity of pathophysiology in neurosurgical patient populations are important to consider in evaluating the risks and benefits of IIT. While extremes of glucose levels are to be avoided, there are little data to support specific use of IIT for maintenance of euglycemia in the perioperative management of neurosurgical patients. Existing data are summarized and reviewed in this context.

Models of traumatic cerebellar injury

Traumatic brain injury (TBI) is a major cause of morbidity and mortality worldwide. Studies of human TBI demonstrate that the cerebellum is sometimes affected even when the initial mechanical insult is directed to the cerebral cortex. Some of the components of TBI, including ataxia, postural instability, tremor, impairments in balance and fine motor skills, and even cognitive deficits, may be attributed in part to cerebellar damage. Animal models of TBI have begun to explore the vulnerability of the cerebellum. In this paper, we review the clinical presentation, pathogenesis, and putative mechanisms underlying cerebellar damage with an emphasis on experimental models that have been used to further elucidate this poorly understood but important aspect of TBI. Animal models of indirect (supratentorial) trauma to the cerebellum, including fluid percussion, controlled cortical impact, weight drop impact acceleration, and rotational acceleration injuries, are considered. In addition, we describe models that produce direct trauma to the cerebellum as well as those that reproduce specific components of TBI including axotomy, stab injury, in vitro stretch injury, and excitotoxicity. Overall, these models reveal robust characteristics of cerebellar damage including regionally specific Purkinje cell injury or loss, activation of glia in a distinct spatial pattern, and traumatic axonal injury. Further research is needed to better understand the mechanisms underlying the pathogenesis of cerebellar trauma, and the experimental models discussed here offer an important first step toward achieving that objective.

Toxin-produced Purkinje cell death: a model for neural stem cell transplantation studies

Purkinje cell loss is the hallmark of the cerebellar ataxias. Here the fungal neurotoxin Penitrem A was used to create partially Purkinje-cell-deficient cerebella in neonate and young adult rats suitable for use in neural stem cell transplantation studies. I.p. administration of Penitrem A to P3, P6 and 11-week old rats caused noticeable tremor in all treated animals that lasted between 1 and 3 days and was more immediate in the rat pups than in the 11-week old rats. Quantification of cresyl violet stained sections showed that Purkinje cells were preferentially lost in the cerebellar vermis and specifically in folia VI to IX (P<0.001-0.05). No change occurred in Purkinje cell number in folia I-III and folium X. These results were confirmed by the loss of calbindin binding cells in the Purkinje cell layer and the appearance of enlarged vacuolated mitochondria. The results of the present study show that the Penitrem A can remove Purkinje cells in the immature rat cerebellum and thus provide a potential model to study the micro-environmental cues in vivo for the differentiation of Purkinje cells from transplanted and/or intrinsic neural stem cells.