Crossed cerebellar diaschisis accompanied by hemiataxia: a PET study

Ataxic hemiparesis: a narrative review for clinical practice in rehabilitation

BACKGROUND

Ataxic hemiparesis (AH) is a well-recognized clinical lacunar stroke syndrome, characterized by paresis with ataxia on the same side of the body. It affects patients with stroke involving the basal ganglia, pons, internal capsule, corona radiata, and thalamus. In the past, lacunar syndrome denotes good functional recovery with low mortality and morbidity rate. However, recent evidence suggests AH has an association with more debilitating outcomes in the long term.

OBJECTIVE

To provide a comprehensive narrative review of published literatures on the topics related with AH and update clinical practice including rehabilitation.

METHODS

Literature review was performed by using the keywords "Subcortical Ataxia," "Lacunar Stroke," "Diaschisis", and "Ataxic Hemiparesis" on PubMed and Google Scholar Engines from 1978 to 2022. All papers published in English were reviewed and manual search of references from retrieved literature was performed for other relevant articles.

RESULTS

A comprehensive review was carried out on the following topics: neuroanatomical localization, pathogenesis, clinical features and clinical assessment scales, pharmacological and non-pharmacological modalities for ataxia treatment, prognosis, and outcome.

CONCLUSION

AH imposes significant challenges on stroke survivors when it comes to remediation of balance and coordination. It is associated with increased risk of mortality, stroke recurrence, and dementia. Though application of the concept of neuroplasticity and the utilization of repetitive transcranial magnetic stimulation have shown early promising results, further research is needed to establish the practice guidelines for rehabilitation of patients with AH.

[A case of Holmes tremor in which 123I-IMP SPECT and MRI findings suggest damage to the cerebellothalamic tract and the dentato-rubro-olivary pathway]

A 75-year-old woman was referred to our department in October 2022 with ataxia and involuntary movements of the right upper and lower limbs. She had experienced a left pontine hemorrhage in March 2021, which was managed conservatively. However, she had residual right-sided hemiplegia. In addition, she had cerebellar ataxia and a 2 ‍Hz resting tremor of the right upper and lower limbs, which was enhanced while maintaining posture and contemplation. Based on her history, and the findings of MRI and nuclear medicine imaging, we diagnosed the patient with Holmes tremor due to pontine hemorrhage. Holmes tremor is a rare movement disorder secondary to brainstem and thalamic lesions, characterized by a unilateral low-frequency tremor. In this case, 123I-IMP SPECT and MRI shows damage to the cerebellothalamic tract and dentaro-rubro-olivary pathway.

Effects of intravascular photobiomodulation on cognitive impairment and crossed cerebellar diaschisis in patients with traumatic brain injury: a longitudinal study

The association between intravascular photobiomodulation (iPBM) and crossed cerebellar diaschisis (CCD) and cognitive dysfunction in patients with traumatic brain injury (TBI) remains unknown. We postulate that iPBM might enable greater neurologic improvements. The objective of this study was to evaluate the clinical impact of iPBM on the prognosis of patients with TBI. In this longitudinal study, patients who were diagnosed with TBI were recruited. CCD was identified from brain perfusion images when the uptake difference of both cerebella was > 20%. Thus, two groups were identified: CCD( +) and CCD( -). All patients received general traditional physical therapy and three courses of iPBM (helium-neon laser illuminator, 632.8 nm). Treatment assemblies were conducted on weekdays for 2 consecutive weeks as a solitary treatment course. Three courses of iPBM were performed over 2-3 months, with 1-3 weeks of rest between each course. The outcomes were measured using the Rancho Los Amigos Levels of Cognitive Functioning (LCF) tool. The chi-square test was used to compare categorical variables. Generalized estimating equations were used to verify the associations of various effects between the two groups. p < 0.05 indicated a statistically significant difference. Thirty patients were included and classified into the CCD( +) and CCD( -) groups (n = 15, each group). Statistics showed that before iPBM, CCD in the CCD( +) group was 2.74 (exp 1.0081) times higher than that of CCD( -) group (p = 0.1632). After iPBM, the CCD was 0.64 (exp-0.4436) times lower in the CCD( +) group than in the CCD( -) group (p < 0.0001). Cognitive assessment revealed that, before iPBM, the CCD( +) group had a non-significantly 0.1030 lower LCF score than that of CCD( -) group (p = 0.1632). Similarly, the CCD( +) group had a non-significantly 0.0013 higher score than that of CCD( -) after iPBM treatment (p = 0.7041), indicating no significant differences between the CCD( +) or CCD( -) following iPBM and general physical therapy. CCD was less likely to appear in iPBM-treated patients. Additionally, iPBM was not associated with LCF score. Administration of iPBM could be applied in TBI patients to reduce the occurrence of CCD. The study failed to show differences in cognitive function after iPBM, which still serves as an alternative non-pharmacological intervention.

Crossed cerebellar diaschisis in Alzheimer's disease

BACKGROUND

Crossed cerebellar diaschisis (CCD) is characterized by hypometabolism and hypoperfusion on molecular imaging in the cerebellum due to a supratentorial lesion on the contralateral side. CCD is a well-established phenomenon in acute or subacute conditions such as infarction but it has been less well described in chronic conditions such as neurodegenerative dementias. Here, we investigate CCD in a large sample of 830 people meeting research criteria for Alzheimer's disease (AD) using [18F]fluorodeoxyglucose-positron emission tomography (FDG-PET).

MATERIALS AND METHODS

This study is based on FDG-PET data collected at baseline as part of two large-scale Phase III clinical trials of a novel tau aggregation inhibitor medication, methylthioninium in mild to moderate AD participants. Quantification of FDG-PET hypometabolism was carried out using standardized uptake value ratio (SUVR), with the pons as the comparison region. SUVR was compared in different regions of interest between the right and left hemispheres of the brain and cerebellum in people with mild AD (Mini-Mental State Examination score ≥ 20).

RESULTS

Comparison of SUVR in different brain regions demonstrated significant differences in the temporal, occipital and cerebellar cortices. Right and left asymmetry was noted with lower SUVR in the left temporal and occipital regions, whereas SUVR was lower in the right side of the cerebellum.

CONCLUSION

Here, we found robust evidence of CCD in a large sample of people with AD, a chronic neurodegenerative condition. The presence of this phenomenon in AD opens up a new avenue of research in AD pathogenesis and has the potential to change future diagnostic and therapeutic strategies.

Crossed Cerebellar Diaschisis in Alzheimer's Disease Detected by Arterial Spin-labelling Perfusion MRI

BACKGROUND

Crossed cerebellar diaschisis (CCD) is a phenomenon with depressed metabolism and hypoperfusion in the cerebellum. Using arterial spin-labelling perfusion weighted magnetic resonance imaging (ASL PWI), we investigated the frequency of CCD in patients with Alzheimer's disease (AD) and differences between patients with and without CCD.

PATIENTS AND METHODS

In patients with AD who underwent a standardized magnetic resonance imaging including ASL PWI cerebral blood flow was evaluated in the cerebellum, and brain segmentation/volumetry was performed using mdbrain (mediaire GmbH, Berlin, Germany) and FSL FIRST (Functional Magnetic Resonance Imaging of the Brain Software Library).

RESULTS

In total, 65 patients were included, and 22 (33.8%) patients were assessed as being CCD-positive. Patients with CCD had a significantly smaller whole brain volume (862.8±49.9 vs. 893.7±62.7 ml, p=0.049) as well as white matter volume (352.9±28.0 vs. 374.3±30.7, p=0.008) in comparison to patients without CCD.

CONCLUSION

It was possible to detect CCD by ASL PWI in approximately one-third of patients with AD and was associated with smaller whole brain and white matter volume.

Novel quantitative approach for crossed cerebellar diaschisis detection in acute ischemic stroke using CT perfusion

PURPOSE

Crossed cerebellar diaschisis (CCD) is a common finding in hyper-acute ischemic stroke, related to supratentorial dysfunction of the contralateral hemisphere. Several studies investigated a possible relationship between CCD and clinical outcomes but still no evidence emerged. We proposed a novel quantitative whole cerebellum analysis using CT perfusion (CTP) imaging to investigate the relationship between CCD and stroke severity, hypoperfused volume and outcome measures.

METHODS

55 patients with supratentorial ischemic stroke who underwent CTP evaluation within 4.5 h since symptom onset were enrolled. CCD was evaluated by CTP image-processing and by calculating the mean transit time (MTT)-map asymmetry index in the whole cerebellum. MTT asymmetry correlation with ischemic volume and clinical outcomes was investigated.

RESULTS

MTT asymmetry was found in most of the included patients and significantly correlated with NIH Stroke Scale (NIHSS) score at baseline and CTP ischemic volume. MTT asymmetry was significantly correlated with hemorrhagic transformation, NIHSS and modified Rankin Scale (mRS) score on discharge in treated patients.

CONCLUSIONS

CCD was detectable by CTP in acute supratentorial ischemic stroke by processing the whole cerebellum volume. CCD perfusion asymmetry was significantly correlated with neurological and perfusion deficit on admission as well as with clinical outcomes in treated patients.

Detection of subthreshold atrophy in crossed cerebellar degeneration via two-compartment mathematical modeling of cell density in DWI: A proof of concept study

Crossed cerebellar diaschisis (CCD) refers to transneuronal degeneration of the corticopontocerebellar pathway, resulting in atrophy of cerebellum contralateral to supratentorial pathology. CCD is traditionally diagnosed on nuclear medicine studies. Our aim is to apply a biexponential diffusion model, composed of intracellular and extracellular compartments, to the detection of subthreshold CCD on DWI, with the calculated fraction of the intracellular compartment as a proposed measure of cell density. At a voxel-by-voxel basis, we solve for intracellular and extracellular coefficients in each side of the cerebellum and compare the distribution of coefficients between each hemisphere. We demonstrate, in all six CCD cases, a significantly lower contribution of the intracellular compartment to the cerebellar hemisphere contralateral to supratentorial pathology (p < 0.01). In a separate, proof-of-concept case of pontine stroke, we also demonstrate reduced intracellular coefficients in bilateral cerebellar hemispheres, excluding middle cerebellar peduncles (p < 0.01). Our findings are consistent with a decreased intracellular fraction, presumably a surrogate for reduced cellular density in corticopontocerebellar degeneration, despite normal-appearing scans. Our approach allows detection of subthreshold structural changes and offers the additional advantage of applicability to most clinical cases, where only three DWI beta values are available.

Familial and sporadic chronic progressive degenerative parietal ataxia

BACKGROUND & OBJECTIVE

Parietal ataxia has been mainly reported as a consequence of acute ischemic stroke, while degenerative parietal ataxia has not been reported.

METHODS

We investigated clinical characteristics, neuroimaging data, and genetic analysis of patients with cerebellar ataxia plus parietal atrophy.

RESULTS

We identified seven patients, including five patients from two families, with chronic progressive cerebellar ataxia due to degenerative parietal atrophy but not stroke. Age at onset of ataxia was 57.6 ± 6.9 years. All patients showed chronic progressive cerebellar ataxia with severity of ataxic gait > limb ataxia > dysarthria. Patients showed no cognitive dysfunction, muscle weakness, or parkinsonism, and only two patients showed mild sensory disturbances. The seven patients showed lateralized limb ataxia with greater contralateral parietal lobe atrophy by magnetic resonance imaging, and hypoperfusion by single photon emission computed tomography, without any abnormal cerebellar pathology (i.e., crossed cerebellar diaschisis). Pathogenic mutations in the microtubule-associated protein tau gene were not found using two single nucleotide polymorphisms.

CONCLUSIONS

This is the first description showing unique clinical features of familial and sporadic chronic progressive degenerative parietal ataxia.

Combination Treatment of Low-Frequency Repetitive Transcranial Magnetic Stimulation and Intensive Occupational Therapy for Ataxic Hemiparesis due to Thalamic Hemorrhage

Background

Both low-frequency repetitive transcranial magnetic stimulation (LF-rTMS) and intensive occupational therapy (OT) are clinically beneficial for post-stroke patients with upper-limb hemiparesis. However, the usefulness of LF-rTMS and intensive OT for ataxic hemiparesis (AH) is unknown.

Methods

The study subjects included 7 patients with AH. All patients had ataxia and mild hemiparesis without a sensory disturbance that was due to thalamic hemorrhage. Each patient was scheduled to receive 20-min rTMS at 1 Hz at the contralesional cerebral hemisphere followed by 120-min intensive OT, daily for 21 sessions. The primary outcome was the motor function of the affected upper limb that was evaluated by using the Fugl-Meyer Assessment (FMA). In addition, the International Cooperative Ataxia Rating Scale (ICARS) score was determined to assess the severity of ataxia.

Results

All patients completed the protocol without any adverse effects. The FMA score significantly increased after treatment. Notably, the ICARS score also significantly decreased.

Conclusions

Our proposed combination treatment is a safe and feasible neurorehabilitative intervention for patients with AH due to thalamic hemorrhage. Our results demonstrate the possibility that rTMS in combination with intensive OT could improve motor function and alleviated ataxia in patients with AH.

Postural asymmetry correlated with lateralization of cerebellar perfusion in persons with chronic stroke: A role of crossed cerebellar diaschisis in left side

OBJECTIVE

Hemiplegia after stroke leads to impairment of the affected limbs and induces more weight on the non-paretic lower limb to form postural asymmetry. Studies of asymmetric cerebral functions have found similarly asymmetric functions in the cerebellum. Crossed cerebellar diaschisis (CCD) is defined as reduced blood flow and hypometabolism in the cerebellar hemisphere contralateral to supratentorial cerebral pathology. No study explored the relationship between posture (standing balance) and CCD in those persons yet. It was hypothesized that CCD would impair postural control and tend toward lateralization of cerebellar perfusion.

METHODS

To determine the relationship between postural asymmetry and CCD among patients with chronic stroke while testing in the upright position. Based on images from Tc-99m-ECD brain perfusion, 42 patients were retrospectively allocated into three groups: left CCD, right CCD and no CCD. The ability to maintain an upright stance as assessed by postural parameters was evaluated using a force platform.

RESULTS

The sway intensity differed significantly between the groups with left CCD and no CCD (p = 0.0052), as did the sway velocities (p = 0.0010). The association between the duration of stroke and sway intensity was highly significant (p < 0.0001). The interval from the stroke onset to the postural analysis was significantly associated with sway intensity and velocity.

CONCLUSIONS

This study indicates that the impairment of posture sway control was more severe in left CCD than the other CCD types. The results support a relationship between the postural asymmetry and lateralization of CCD in patients with chronic stroke.

Value of dynamic susceptibility contrast perfusion MRI in the acute phase of transient global amnesia

PURPOSE

Transient global amnesia (TGA) is a transitory, short-lasting neurological disorder characterized by a sudden onset of antero- and retrograde amnesia. Perfusion abnormalities in TGA have been evaluated mainly by use of positron emission tomography (PET) or single-photon emission computed tomography (SPECT). In the present study we explore the value of dynamic susceptibility contrast perfusion-weighted MRI (PWI) in TGA in the acute phase.

METHODS

From a MRI report database we identified TGA patients who underwent MRI including PWI in the acute phase and compared these to control subjects. Quantitative perfusion maps (cerebral blood flow (CBF) and volume (CBV)) were generated and analyzed by use of Signal Processing In NMR-Software (SPIN). CBF and CBV values in subcortical brain regions were assessed by use of VOI created in FIRST, a model-based segmentation tool in the Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB) Software Library (FSL).

RESULTS

Five TGA patients were included (2 men, 3 women). On PWI, no relevant perfusion alterations were found by visual inspection in TGA patients. Group comparisons for possible differences between TGA patients and control subjects showed significant lower rCBF values bilaterally in the hippocampus, in the left thalamus and globus pallidus as well as bilaterally in the putamen and the left caudate nucleus. Correspondingly, significant lower rCBV values were observed bilaterally in the hippocampus and the putamen as well as in the left caudate nucleus. Group comparisons for possible side differences in rCBF and rCBV values in TGA patients revealed a significant lower rCBV value in the left caudate nucleus.

CONCLUSIONS

Mere visual inspection of PWI is not sufficient for the assessment of perfusion changes in TGA in the acute phase. Group comparisons with healthy control subjects might be useful to detect subtle perfusion changes on PWI in TGA patients. However, this should be confirmed in larger data sets and serial PWI examinations.

Crossed cerebellar diaschisis in acute isolated thalamic infarction detected by dynamic susceptibility contrast perfusion MRI

PURPOSE

Crossed cerebellar diaschisis (CCD) is a state of neural depression caused by loss of connections to injured neural structures remote from the cerebellum usually evaluated by positron emission tomography. Recently it has been shown that dynamic susceptibility contrast perfusion weighted MRI (PWI) may also be feasible to detect the phenomenon. In this study we aimed to assess the frequency of CCD on PWI in patients with acute thalamic infarction.

METHODS

From a MRI report database we identified patients with acute isolated thalamic infarction. Contralateral cerebellar hypoperfusion was identified by inspection of time to peak (TTP) maps and evaluated quantitatively on TTP, mean transit time (MTT), cerebral blood flow and volume (CBF, CBV) maps. A competing cerebellar pathology or an underlying vascular pathology were excluded.

RESULTS

A total of 39 patients was included. Common symptoms were hemiparesis (53.8%), hemihypaesthesia (38.5%), dysarthria (30.8%), aphasia (17.9%), and ataxia (15.4%). In 9 patients (23.1%) PWI showed hypoperfusion in the contralateral cerebellar hemisphere. All of these had lesions in the territory of the tuberothalamic, paramedian, or inferolateral arteries. Dysarthria was observed more frequently in patients with CCD (6/9 vs. 6/30; OR 8.00; 95%CI 1.54-41.64, p = 0.01). In patients with CCD, the median ischemic lesion volume on DWI (0.91 cm³), IQR 0.49-1.54 cm³) was larger compared to patients with unremarkable PWI (0.51 cm³, IQR 0.32-0.74, p = 0.05). The most pronounced changes were found in CBF (0.94±0.11) and MTT (1.06±0.13) signal ratios, followed by TTP (1.05±0.02).

CONCLUSIONS

Multimodal MRI demonstrates CCD in about 20% of acute isolated thalamic infarction patients. Lesion size seems to be a relevant factor in its pathophysiology.

Nuclear medicine in cerebrovascular disease

Stroke and cerebrovascular diseases are major causes of mortality, morbidity, and disability. Nuclear Medicine, primarily via tomographic methods, has made significant contributions to the understanding of the hemodynamic and metabolic consequences of cerebrovascular diseases. In this review, the findings in acute, subacute, and chronic cerebrovascular diseases are described. Many of the pathophysiologic processes and consequences that follow stroke, including completed infarct core, adjacent penumbra, and diaschisis, have been investigated with Nuclear Medicine, and stroke outcome may be related to these phenomena. Additional topics included in this review are cerebrovascular reserve tests and multi-infarct dementia. Finally, Nuclear Medicine investigations of stroke recovery and cerebral plasticity appear to indicate that enhanced activity of preexisting networks, rather than substitution of function, represents the most important mechanism of improvement in chronic stroke rehabilitation.

Upside down crossed cerebellar diaschisis: proposing chronic stimulation of the dentatothalamocortical pathway for post-stroke motor recovery

BACKGROUND

Stroke remains the leading cause for long-term motor impairment in the industrialized world. New techniques are needed to improve outcomes.

OBJECTIVE

To propose chronic electrical stimulation of the dentatothalamocortical pathway as a method for enhancing cortical excitability and improving motor recovery following stroke.

METHOD

In previous studies, motor evoked potentials were derived from intracortical microstimulation and used to index cortical excitability in rats undergoing continuous, asynchronous deep cerebellar stimulation. In a separate set of experiments, the effect of chronic deep cerebellar stimulation on motor recovery was tested in rats following large ischemic strokes.

RESULTS

Deep cerebellar stimulation modulated cortical excitability in a frequency-dependent fashion. Beta band stimulation yielded sustained increment in excitability and was associated with enhanced motor recovery compared to sham stimulation.

CONCLUSION

Chronic deep cerebellar stimulation enhances recovery of motor function following large ischemic strokes in the rat, an effect that may be associated with increased cortical excitability. Given that deep brain stimulation is already a well established method, this new approach to motor recovery may be a viable option for human translation in stroke rehabilitation.

Gait ataxia in essential tremor is differentially modulated by thalamic stimulation

Patients with advanced stages of essential tremor frequently exhibit tandem gait ataxia with impaired balance control and imprecise foot placement, resembling patients with a cerebellar deficit. Thalamic deep brain stimulation, a surgical therapy for otherwise intractable cases, has been shown to improve tremor, but its impact on cerebellar-like gait difficulties remains to be elucidated. Eleven patients affected by essential tremor (five females; age 69.8 ± 3.9 years; disease duration 24.4 ± 11.2 years; follow-up after surgery 24.7 ± 20.3 months) were evaluated during the following conditions: stimulation off, stimulation on and supra-therapeutic stimulation. Ten age-matched healthy controls served as the comparison group. Locomotion by patients and controls was assessed with (i) overground gait and tandem gait; (ii) balance-assisted treadmill tandem gait and (iii) unassisted treadmill gait. The two treadmill paradigms were kinematically analysed using a 3D opto-electronic motion analysis system. Established clinical and kinesiological measures of ataxia were computed. During stimulation off, the patients exhibited ataxia in all assessment paradigms, which improved during stimulation on and worsened again during supra-therapeutic stimulation. During over ground tandem gait, patients had more missteps and slower gait velocities during stimulation off and supra-therapeutic stimulation than during stimulation on. During balance-assisted tandem gait, stimulation on reduced the temporospatial variability in foot trajectories to nearly normal values, while highly variable (ataxic) foot trajectories were observed during stimulation off and supra-therapeutic stimulation. During unassisted treadmill gait, stimulation on improved gait stability compared with stimulation off and supra-therapeutic stimulation, as demonstrated by increased gait velocity and ankle rotation. These improvements in ataxia were not a function of reduced tremor in the lower limbs or torso. In conclusion, we demonstrate the impact of thalamic stimulation on gait ataxia in patients with essential tremor with improvement by stimulation on and deterioration by supra-therapeutic stimulation, despite continued control of tremor. Thus, cerebellar dysfunction in these patients can be differentially modulated with optimal versus supra-therapeutic stimulation. The cerebellar movement disorder of essential tremor is due to a typical cerebellar deficit, not to trembling extremities. We hypothesize that deep brain stimulation affects two major regulating circuits: the cortico-thalamo-cortical loop for tremor reduction and the cerebello-thalamo-cortical pathway for ataxia reduction (stimulation on) and ataxia induction (supra-therapeutic stimulation).

Clinical and topographic magnetic resonance imaging characteristics of suspected thalamic infarcts in 16 dogs

Sixteen dogs with acute-onset, non-progressive signs of brain dysfunction and magnetic resonance imaging (MRI) characteristics compatible with thalamic infarction are described. Topographically the MRI lesions could be grouped in three thalamic regions, namely, paramedian (8/16), extensive dorsal (5/16) and ventrolateral (3/16). Paramedian lesions resulted in signs typical of vestibular dysfunction. Extensive dorsal lesions were associated with vestibular ataxia, circling and contralateral menace response deficits. Ventrolateral lesions resulted in circling and contralateral proprioceptive deficits. In several dogs, regions other than the thalamus were also affected: four extended into the midbrain; six extended to the internal capsule, and two dogs had a second lesion in the cerebellum. Three clinical syndromes were identified in association with thalamic infarction. These signs varied somewhat, most likely because lesions were not confined to specific nuclear boundaries and involved different combinations of thalamic nuclei.

Isolated Hemiataxia and Cerebellar Diaschisis after a Small Dorsolateral Medullary Infarct

Isolated hemiataxia after a medullary infarct is rare. We describe a case of isolated hemiataxia after a small infarct localized at the ipsilateral dorsolateral medulla. An 83-year-old man developed acute onset of ataxia in the left arm and in both legs. Speech and extraocular movement were normal, and he did not have any other neurological manifestations. Brain MRI showed a small infarct localized at the left dorsolateral medulla, which involved the inferior cerebellar peduncle. (123)ECD-SPECT showed hypoperfusion in the left cerebellar hemisphere without clear vascular territory. Neuroimaging findings for our patient suggested the involvement of the inferior cerebellar peduncle that projects to the cerebellum in our patient.

Diffusion weighted imaging in ataxic hemiparesis

OBJECTIVE

Ataxic hemiparesis (AH) is a well recognised lacunar syndrome involving homolateral ataxia with accompanying corticospinal tract impairment. Most previous studies of lesion location in AH did not use diffusion weighted MRI (DW MRI). The purpose of this study was to use DW MRI to evaluate the radiological correlation in patients presenting with AH.

METHODS

Retrospectively, we studied 29 patients with AH using DW MRI.

RESULTS

All patients were scanned within 4 days of onset. Acute infarction was identified in 28 of 29 (97%) patients. A single lesion was identified in 26

PATIENTS

pons (n = 8), internal capsule (n = 6), corona radiata (n = 2), distended internal capsule from corona radiate (n = 7), frontal subcortical area (n = 1) and precentral with or without postcentral gyrus (n = 2). Two lesions were found in two patients: in the pons and corpus callosum of one patient, and in the corona radiata and subcortical white matter of the other.

CONCLUSIONS

AH is mainly caused by pontine or internal capsule/corona radiata lesions. It also occurs in the precentral gyrus, including the precentral knob, with or without postcentral gyrus lesions. Fibres of the fronto-ponto-cerebellar system may originate from the frontal cortex, including the precentral gyrus, probably near the pyramidal tract. Damage at this location may cause AH.

Ataxic hemiparesis from strategic frontal white matter infarction with crossed cerebellar diaschisis

BACKGROUND

Ataxic hemiparesis is a classic lacunar syndrome that most often localizes to the pons.

RESULTS

We report 3 patients who presented with left-sided ataxic hemiparesis and were found on imaging to have small right frontal subcortical white matter infarcts in similar locations by diffusion-weighted MRI. [99mTc]hexamethylpropylenamine oxime single-photon emission computed tomography (SPECT) scans in all 3 patients showed decreased metabolism in the contralateral cerebellar hemisphere, indicative of crossed cerebellar diaschisis (CCD).

CONCLUSIONS

CCD is under-recognized in ataxic hemiparesis and may have implications for functional recovery after this type of ischemic stroke.

Correlation of interictal spike-wave with thalamic glucose metabolism in juvenile myoclonic epilepsy

The purpose of this study is to define metabolic correlates of generalized spike-wave discharges in juvenile myoclonic epilepsy. We investigated the alterations in glucose metabolism and possible correlations between the interictal epileptiform discharges and regional metabolism in patients with juvenile myoclonic epilepsy using a combined positron emission tomography/electroencephalography method. We found that the thalamic metabolism is slightly increased interictally in the patient group compared with controls. We also observed significant positive correlations between the amount of spike-wave activity and thalamic metabolism. Our results provide evidence that the thalamus has an important role in the generation of spontaneous generalized spike-wave discharges in juvenile myoclonic epilepsy.

Thalamic infarct presenting with thalamic astasia

Astasia, inability to stand unsupported despite good strength, resembles the marked balance impairment of patients with vestibulocerebellar disease. We describe a patient with unilateral thalamic infarct that presented with astasia. A 76-year-old hypertensive woman was admitted to our hospital because of marked unsteadiness. On neurological examination, she could not stand unsupported and the woman's body swayed back and forth markedly. The swaying was not compensated for by her taking a step forward or backward, and she frequently collapsed when support was withdrawn. Diffusion-weighted magnetic resonance image revealed a discrete infarct within the right posterolateral thalamus. Brain single photon emission computerized tomography revealed markedly decreased regional cerebral blood flow within in the right thalamus with concomitant left superior cerebellar region. We discuss the possible pathomechanisms of thalamic astasia.

Occipital Hypometabolism Demonstrated by Positron Emission Tomography After Temporal Lobectomy for Refractory Epilepsy

BACKGROUND

Epilepsy surgery involves well-planned discrete injury to the brain and may create visual deficits. This study seeks to evaluate the indirect effects of temporal lobectomy on brain metabolism by correlating visual field defects and glucose metabolism in the visual cortex of patients before and after undergoing epilepsy surgery.

METHODS

A retrospective survey of 11 patients who had undergone temporal lobectomy for refractory epilepsy in a single institution from 1986 to 1989, and who had pre-lobectomy and post-lobectomy visual field examinations and F-18 2-fluorodeoxyglucose positron emission tomography (FDG-PET) as part of a standard comprehensive epilepsy surgery evaluation. The PET images were analyzed to provide a correlation with the visual field defects that developed after the temporal lobectomy.

RESULTS

Occipital hypometabolism in the absence of structural lesions of the occipital lobe was noted in seven patients with contralateral visual field defects and in one of four patients without a visual field defect. FDG-PET studies in three patients repeated for as long as 20 months after lobectomy showed no significant change in the occipital hypometabolism pattern.

CONCLUSIONS

Although the occipital cortex was not directly injured during temporal lobectomy, the resulting hypometabolism correlates with the clinical findings of visual field defects. The hypometabolism may be due to deafferentation after interruption of the optic pathways and appears to be persistent.

Involvement of the cerebellar thalamus in human saccade adaptation

Saccade adaptation can be experimentally induced by systematically displacing a visual cue during a targeting saccade. Non-human primate studies have highlighted the crucial role of the cerebellum for saccade adaptation, but its neural substrates in humans are poorly understood. Recent physiological experiments suggest that, in addition to cerebellar structures, cortical areas may be involved as well. We have therefore hypothesized that saccade adaptation may rely on a cerebello-cerebral network, in which the cerebellar thalamus may link cerebellar and cerebral structures. To test this hypothesis, we studied saccade adaptation in a group of four patients with a thalamic lesion, with (n = 2) or without (n = 2) involvement of the cerebellar thalamus. Compared to healthy subjects, saccade adaptation was reduced in patients with associated cerebellar syndrome, but normal in patients without cerebellar syndrome. These results are consistent with the hypothesis that cerebello-thalamic pathways contribute to saccade adaptation in humans and suggest that the thalamus relays adaptation-related information from the cerebellum to cerebral cortical oculomotor areas.

Single photon emission computed tomography in tuberculous meningitis

INTRODUCTION

Data on single photon emission computed tomography (SPECT) in tuberculous meningitis are lacking and prompted this study. SPECT findings in tuberculous meningitis are reported and correlated with clinical and radiological findings.

PATIENTS AND METHODS

Seventeen patients with tuberculous meningitis that was diagnosed on clinical, radiological, and laboratory criteria have been included. Their age ranged between 5 and 62 years and four of them were female. Computed tomography and/or magnetic resonance imaging (MRI) and SPECT using (99m)Tc-ethylene cystine dimer were performed in all the patients. On the basis of Barthel index (BI) score the patients' outcome was defined as complete (BI = 20), partial (BI = 19-12), and poor recovery (BI<12).

RESULT

Eleven patients were in stage III and three each in stage II and stage I tuberculous meningitis. Two patients had hemiplegia and five quadriplegia. Computed tomography was abnormal in 11 out of 16 patients and revealed hydrocephalus in nine, basal exudates, infarction in subcortical white matter and basal ganglia in six patients each, frontal cortical infarction in one, and granulomata in three patients. Cranial MRI was carried out in four patients and revealed multiple granulomata, hydrocephalus, and brainstem infarction in two patients each. SPECT studies were abnormal in all except two patients and revealed hypoperfusion of the basal ganglia in 14, cortical hypoperfusion in 10, and midbrain hypoperfusion in one patient. At the three month follow up four patients had died, five had poor, three partial, and five complete recovery. The SPECT studies were more frequently abnormal compared with computed tomography but did not correlate with stage of meningitis or outcome.

CONCLUSION

In tuberculous meningitis subcortical and cortical hypoperfusion is common but it does not correlate with stage of meningitis or three month outcome.

Early serial SPET in acute middle cerebral artery infarction

The size and severity of perfusion defects in acute cerebral ischaemia on single photon emission tomographic (SPET) images may provide useful information regarding long-term (> 3 month) stroke outcome. A decreased predictive value has been reported with delayed SPET more than 24 h after stroke onset. We examined 20 patients with acute middle cerebral artery (MCA) infarctions using serial 99Tcm-ECD or 99Tcm-HMPAO SPET (SPET 1 one day and SPET 2 three days after stroke onset). Neurological (NIH, SSS) and functional (Barthel, Rankin) scores were calculated simultaneously and 3 months poststroke. The two SPET scans correlated equally well with the severity of functional and neurological deficits evaluated 3 months after stroke onset. In comparison to clinical assessment, the prognostic value of SPET was relatively better on the first day than the third day. Crossed cerebellar diaschisis correlated with early SPET deficits, but did not predict functional outcome. Our results suggest that SPET, either with 99Tcm-ECD or 99Tcm-HMPAO, can be used to predict stroke outcome in acute MCA infarction up to 72 h poststroke without significant interference from luxury perfusion.

Effects of amphetamines and small related molecules on recovery after stroke in animals and man

Drugs modulating the levels of specific central neurotransmitters may influence both the rate and amount of functional recovery after focal brain injuries such as stroke. Because such drugs may be effective long after brain injury, the "therapeutic window" may be widened beyond the first few hour after stroke and an entirely new avenue for pharmacological intervention may be possible. The impact of drugs affecting norepinephrine and gamma-aminobutyric acid have been among the most extensively studied in the laboratory, and preliminary clinical data suggest similar effects in humans.

Crossed cerebellar diaschisis: assessment with dynamic susceptibility contrast MR imaging

The authors investigated the feasibility of using T2-weighted, half-Fourier rapid acquisition with relaxation enhancement, or RARE, dynamic susceptibility contrast magnetic resonance (MR) imaging to depict crossed cerebellar diaschisis. In 10 patients after unilateral supratentorial stroke, crossed cerebellar diaschisis was demonstrated in the relative regional cerebellar blood volume maps obtained with MR imaging. Cerebellar blood volume values for the nonaffected cerebellar hemisphere were significantly larger than those for the affected side (P = .0003).

Dissociation of frontal and cerebellar activity in a cognitive task: evidence for a distinction between selection and search

Human brain imaging studies have found that increases in functional activation in left-frontal cortex during cognitive tasks are often accompanied by similar increases in right-cerebellar regions. The present study used functional magnetic resonance imaging (fMRI) to investigate the distinctive contributions of these regions using a word stem completion task. Stems with many possible completions (MANY condition) were alternately presented with stems that had few possible completions (FEW condition), and subjects were asked to covertly complete each stem with a word and press a response switch for each successful completion. Prominent increases in activation in the MANY, relative to the FEW, condition were observed in the left middle frontal gyrus (Brodmann areas 9/10) and left caudate nucleus. In contrast, portions of the right-cerebellar hemisphere (posterior quadrangular lobule and superior semilunar lobule) and cerebellar vermis exhibited increases in the FEW, relative to the MANY, condition. This double dissociation suggests that the frontal and cerebellar regions make distinctive contributions to cognitive performance, with left-frontal (and striatal) activations reflecting response selection, which increases in difficulty when there are many appropriate responses, and right-cerebellar activation reflecting the search for responses, which increases in difficulty when even a single appropriate response is hard to retrieve.

Clinical significance of reduced cerebral metabolism in multiple sclerosis: a combined PET and MRI study

Magnetic resonance imaging (MRI) in patients with multiple sclerosis (MS) has provided major insights into the disease's natural history, and many studies have focussed on possible correlations between MRI findings and the clinical manifestations of MS. In contrast, there are few reports on possible relationships between functional imaging data and cognitive function. The present study assessed the relationship between clinical presentation and combined anatomical and functional imaging data in MS. Twenty patients with definite MS underwent MRI and positron emission tomography (PET) to evaluate cerebral blood flow (rCBF) and oxygen metabolism (rCMRO2). The relationships between these neuroimaging findings and clinical data, including the Expanded Disability Status Scale (EDSS), Mini-mental status scale, Hasegawa Dementia Scale and relapse time, were evaluated with Spearman's rank correlation coefficients. A general reduction in rCBF and rCMRO2 in the gray and white matter were found in the MS patients. EDSS was correlated with the number and size of the lesions on MRI and was negatively correlated with rCMRO2. A correlation between the decrease in rCMRO2 and the level of cognitive impairment was also found. The severity of cerebral hypometabolism was also related to the number of relapses. Morphological and functional findings obtained by MRI and PET are closely related to the clinical status in MS. Our results suggest that measurement of cerebral metabolism in MS has the potential to be an objective marker for monitoring disease activity and to provide prognostic information.

The role of left prefrontal cortex in language and memory

This article reviews attempts to characterize the mental operations mediated by left inferior prefrontal cortex, especially the anterior and inferior portion of the gyrus, with the functional neuroimaging techniques of positron emission tomography and functional magnetic resonance imaging. Activations in this region occur during semantic, relative to nonsemantic, tasks for the generation of words to semantic cues or the classification of words or pictures into semantic categories. This activation appears in the right prefrontal cortex of people known to be atypically right-hemisphere dominant for language. In this region, activations are associated with meaningful encoding that leads to superior explicit memory for stimuli and deactivations with implicit semantic memory (repetition priming) for words and pictures. New findings are reported showing that patients with global amnesia show deactivations in the same region associated with repetition priming, that activation in this region reflects selection of a response from among numerous relative to few alternatives, and that activations in a portion of this region are associated specifically with semantic relative to phonological processing. It is hypothesized that activations in left inferior prefrontal cortex reflect a domain-specific semantic working memory capacity that is invoked more for semantic than nonsemantic analyses regardless of stimulus modality, more for initial than for repeated semantic analysis of a word or picture, more when a response must be selected from among many than few legitimate alternatives, and that yields superior later explicit memory for experiences.

Cerebral hypoperfusion and hypometabolism with altered striatal signal intensity in chorea-acanthocytosis: a combined PET and MRI study

We studied cerebral perfusion and oxygen metabolism in three patients with chorea-acanthocytosis using positron-emission tomography and oxygen-15 labeled O2 and CO2. High-field magnetic resonance imaging also was performed. Regional cerebral blood flow (rCBF) and oxygen metabolism (rCMRO2) were significantly reduced in the caudate and putamen when compared with seven control subjects. Mild but significant reductions of rCBF (lower than the normal control values -2 SD) were found in the bilateral frontal, left temporal and parietal, and bilateral thalamic areas; rCMRO2 was reduced in the bilateral frontal and left temporal areas. Magnetic resonance imaging showed increased signal intensity accompanied by scattered bright spots in the caudate head and putamen on T2-weighted images; decreased signal intensity was shown at these sites on T1-weighted images. These findings were not observed in 10 neurologically normal volunteers and are rare in the common hyperkinetic form of Huntington's disease. Reduced cerebral perfusion and oxygen metabolism seem to be related to the intellectual and personality changes that occur in chorea-acanthocytosis. Combined positron-emission tomography and magnetic resonance imaging studies may improve diagnostic accuracy in patients with chorea-acanthocytosis and related disorders.

Bipolar disorders, dystonia, and compulsion after dysfunction of the cerebellum, dentatorubrothalamic tract, and substantia nigra

Bipolar disorders occurred in 3 of 15 (20%) subjects after focal cerebellar circuit lesions. Two presented with rapid cycling bipolar disorder and dystonia, including one with a checking compulsion. Lesions included right cerebellar hypoplasia (bipolar disorder), bilateral cerebellar atrophy (rapid cycling unipolar mania and dystonia), and left midbrain pathology (mixed bipolar disorder, dystonia, and compulsion). Bipolar disorders were associated with cerebellar circuit pathology (p = 0.032) and were more prevalent than in population controls (p = 0.004). Diminished cerebellar output (to cortical, thalamic, basal ganglia, limbic, or other circuits) or nigral pars reticulata dysfunction may result in abnormal neuronal oscillation in bipolar disorders, especially rapid-cycling types, or in dystonia. Review of the literature supports the concept of nigral and cerebellar direct and indirect connections with thalamofrontotemporal and basal ganglia circuits in bipolar disorders, dystonia, and compulsions, as well as possible clinical relationships between these disorders.

Contribution of diaschisis to the clinical deficit in human cerebral infarction

BACKGROUND AND PURPOSE

Regions of decreased cerebral blood flow are often seen on single-photon emission computed tomography (SPECT) after stroke and have been widely reported to add to the clinical deficit. However, such reports have not distinguished between correlation and causation. We analyzed 124 serial SPECT scans performed in 50 patients to assess the role of diaschisis in the clinical deficit after stroke.

METHODS

SPECT with the use of 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO) was performed in a prospective, unselected series of 50 patients with cerebral infarcts studied at a median of 1.1, 6.8, and 95 days after ictus. Patients were also assessed with the use of the Canadian Neurological Scale, the Barthel Index, a neuropsychological evaluation, and infarct volume measurement.

RESULTS

One hundred twenty-four serial SPECT scans were done in 50 patients. Diaschisis was identified at 168 sites. There was insufficient correlation between diaschisis and the clinical measurements to support the suggestion that diaschisis independently causes clinical deficits beyond those due to the infarct itself. Unlike the clinical status, diaschisis showed little tendency to resolve during the 3-month follow-up period of the study. Several of the instances of correlation were shown to be of a noncausal kind, with both the diaschisis and the clinical deficit being due to the lesion directly; there was no known mechanism for the diaschisis to cause the clinical deficit.

CONCLUSIONS

Diaschisis does not independently add to the clinical deficit after stroke. It is more likely that it simply represents part of the damage done by the stroke.

Crossed cerebellar diaschisis and brain recovery after stroke

BACKGROUND AND PURPOSE

Although crossed cerebellar diaschisis is well recognized after stroke, there is controversy concerning its clinical correlations and serial changes, and little is known about its prognostic value.

METHODS

We studied crossed cerebellar diaschisis and cerebral hypoperfusion in 47 patients with acute middle cerebral cortical infarction using 99mTc-hexamethylpropyleneamine oxime and single-photon emission computed tomography within 72 hours of stroke onset. Thirty-one of these patients had outcome studies at 3 months; 15 of the 31 underwent an additional scan after acetazolamide injection. Tissue loss was determined with computed tomography, performed at outcome in 28 patients. Clinical stroke severity was assessed with the Canadian Neurological Scale and Barthel Index. Cerebellar blood flow asymmetry was studied in 22 healthy, age-matched control subjects.

RESULTS

Cerebellar blood flow asymmetry was significant in patients (mean +/- SE, 9.76 +/- 0.78%; P < .001) but not in control subjects (-0.22 +/- 0.56%). Crossed cerebellar diaschisis was strongly associated with infarct hypoperfusion volume at both acute (regression coefficient +/- SEb, b = 6.76 +/- 0.65; P < .001) and outcome stages (b = 6.13 +/- 0.63; P < .001). Cross-sectionally over the first 72 hours, infarct hypoperfusion volume decreased by 2% for each hour from onset (P < .05), while crossed cerebellar diaschisis remained unchanged. Canadian Neurological Scale score at the acute stage was negatively associated with acute crossed cerebellar diaschisis (b = -0.10 +/- 0.05; P < .05) after allowing for infarct hypoperfusion volume. Crossed cerebellar diaschisis did not change between acute-stage, outcome, and postacetazolamide scans. Acute-stage crossed cerebellar diaschisis predicted outcome Barthel Index score (b = -0.28 +/- 0.14; P = .05) and tissue loss (b = 3.81 +/- 0.96; P < .001) but was no longer an independent prognostic factor after allowing for acute-stage infarct hypoperfusion volume.

CONCLUSIONS

This study shows that crossed cerebellar diaschisis is a functional phenomenon that correlates with both stroke severity and infarct hypoperfusion volume and persists despite neurological recovery. Although acute-stage crossed cerebellar diaschisis has no prognostic value independent of acute-stage hypoperfusion volume, it might indicate the proportion of nutritional to nonnutritional perfusion at the infarct site and hence be useful in the evaluation of reperfusion therapies in the acute stage.

Reduced cerebellar blood flow and oxygen metabolism in spinocerebellar degeneration: a combined PET and MRI study

Fourteen patients with spinocerebellar degeneration (SCD) were subjected to MRI and PET studies. The quantitative MRI data revealed significant cerebellar and pontine atrophy in the patients with olivopontocerebellar atrophy (OPCA), and cerebellar atrophy in the patients with late cerebellar cortical atrophy (LCCA). We failed to demonstrate significant differences in the pons between LCCA patients and normal controls. PET measurements revealed decreases in cerebral oxygen metabolic rate (CMRO2) in the cerebellar hemisphere and vermis in both groups of patients. The markedly decreased cerebral blood flow (CBF) and CMRO2 in the pons were found only in the patients with OPCA. PET data corrected for the tissue shrinkage on the basis of MRI morphometry indicated a net reduction in cerebellar CMRO2 and CBF. The present study has demonstrated that a combination of functional and anatomical data offers further evidence in favour of the current acceptable classification of SCD based on clinicopathological grounds. Our data further suggest that the amount of atrophy in the cerebellum could not fully account for the decreased metabolic rates observed in PET studies.

Contralateral cerebellar hypometabolism: a predictor for stroke outcome?

Contralateral cerebellar hypometabolism (CCH) is a well established remote functional effect of cerebral damage. Because CCH has been reported to be reversible in acute stroke in at least some patients, the value of cerebellar metabolic asymmetry (CbMA; a reflection of the degree of CCH) as a predictor of stroke outcome has been assessed. Measurements of cerebellar oxygen consumption were performed by positron emission tomography (PET) in 16 patients within 5-30 hours of onset of their first ever middle cerebral artery territory stroke, and again 13-56 days later in 12 survivors. The neurological state was quantified at the time of each PET study and at day 60, with both the Mathew and Orgogozo scales. In the early PET study, the CbMAs ranged from around 0% to nearly 50% (individually significant at p < 0.05 in 9/16 patients) but were neither strongly nor consistently correlated with neurological outcome or recovery at day 60. Similarly, the changes in CbMAs from the early to the late PET study were not correlated with the concomitant neurological evolution. At the late PET study, however, there were excellent positive correlations between CbMAs and both neurological status and size of infarction (assessed by CT in the chronic stage). The correlation with neurological status was explained by the correlation with size of infarction. The poor predictive value of CbMAs in the early PET study may be partly because the cerebral metabolic disturbance might still be evolving at this early stage in some cases. Despite this lack of a strong quantitative link between CbMAs at the early PET study and outcome, the outcome was good in all the patients who did not exhibit significant CCH, suggesting that lack of CCH may predict good outcome in acute middle cerebral artery stroke.

Cerebral blood flow and oxygen metabolism in progressive dementia associated with amyotrophic lateral sclerosis

We examined regional cerebral blood flow (rCBF) and oxygen metabolism (rCMRO2) in 4 patients with progressive dementia associated with amyotrophic lateral sclerosis (ALS), in 9 patients with classical ALS without dementia, and in 13 normal controls, using positron emission tomography with oxygen-15 gas and oxygen-15 labeled carbon dioxide. The mean rCBF and rCMRO2 in the anterior cerebral hemispheres decreased significantly in patients with progressive dementia with ALS, compared to those in controls. Patients with only ALS showed very mild reductions of rCBF and rCMRO2 which were not statistically significant. These data suggest that hypoperfusion and oxygen hypometabolism in the anterior cerebral hemispheres have an etiological relationship to deterioration of intellect in patients with progressive dementia with ALS. A significant reduction in the mean rCBF was also found in the cerebellar hemispheres in progressive dementia with ALS, while a reduction of mean rCMRO2 was not significant. Remote effects analogous to crossed cerebellar diaschisis occurring bilaterally were assumed to explain the cerebellar hypoperfusion.

Brain stem infarction and diaschisis. A SPECT cerebral perfusion study

BACKGROUND AND PURPOSE

We studied six patients suffering from pure, unilateral brain stem infarction to explore the association of remote cerebral and cerebellar blood flow changes with damage at different sites of this region of the brain.

METHODS

We used single-photon emission computed tomography and [123I]iodoamphetamine to measure regional differences in tracer uptake. Qualitative image analysis and calculated asymmetry indexes were correlated to the location of the infarcted area on magnetic resonance imaging and to the patients' clinical findings.

RESULTS

Significant perfusion asymmetries were noted in the two patients with infarction in the upper pons but not in those with lesions below this level. They comprised a contralateral cerebellar and ipsilateral supratentorial hypoactivity that was most marked in the frontoparietal cortex. There was no clear relation between the patterns of cerebral or cerebellar tracer uptake and specific neurological findings.

CONCLUSIONS

Remote perfusion changes after pure brain stem infarction may be seen both infratentorially and supratentorially and depend on the lesion site rather than on the neurological deficit. In this context, our study confirmed damage to the corticopontocerebellar pathways as the key event in the genesis of a crossed cerebellar diaschisis. The exact mechanisms causing ipsilateral cerebral hemispheric diaschisis await further clarification.

Cerebellar ataxia in ataxic hemiparesis? A kinematic and EMG analysis

It has recently been proposed that the ataxia in ataxic hemiparesis is a clumsiness common to all patients with hemiparesis and not indicative of any involvement of corticopontocerebellar or cerebellocortical pathways. In disagreement with this view, we report here that a patient with ataxic hemiparesis, following a lesion of the corona radiata, showed the disorders in kinematic and electromyographic (EMG) parameters of goal-directed movements that have recently been demonstrated to be characteristic of patients with cerebellar lesions. This suggests involvement of corticopontocerebellar or cerebellocortical pathways in ataxic hemiparesis.