Topodiagnostic implications of hemiataxia: An MRI-based brainstem mapping analysis

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.

Case Report: Multiple Sclerosis Presenting as Unilateral Gaze-evoked Nystagmus

SIGNIFICANCE

Unilateral gaze-evoked nystagmus is a rare neurologic finding that is largely diagnosed in connection with ischemic stroke. Gazed-evoked nystagmus is also a rare initial presentation of multiple sclerosis.

PURPOSE

This study aimed to report a rare presentation of gaze-evoked nystagmus in a patient with multiple sclerosis and review the mechanism underlying the gaze-evoked nystagmus.

CASE REPORT

A 32-year-old man presented with a 1-week history of diplopia. Neurologic examination revealed right-sided gaze-evoked nystagmus and right-sided ataxia. Laboratory test revealed a positive result for oligoclonal bands. Contrast brain MRI revealed multiple hyperintense T2 lesions including a hyperintense patch at the right inferior cerebellar peduncle. A diagnosis of multiple sclerosis was made. The patient received methylprednisolone 500 mg intravenously for 14 days. The diplopia and gaze-evoked nystagmus resolved and remained stable 2 months later.

CONCLUSIONS

Our case demonstrates that damage to the inferior cerebellar peduncle may result in ipsilesional gaze-evoked nystagmus and ipsilesional ataxia, in contrast to ipsilesional gaze-evoked nystagmus and contralesional ataxia.

Predicting functional outcome in patients with acute brainstem infarction using deep neuroimaging features

BACKGROUND AND PURPOSE

Acute brainstem infarctions can lead to serious functional impairments. We aimed to predict functional outcomes in patients with acute brainstem infarction using deep neuroimaging features extracted by convolutional neural networks (CNNs).

METHODS

This nationwide multicenter stroke registry study included 1482 patients with acute brainstem infarction. We applied CNNs to automatically extract deep neuroimaging features from diffusion-weighted imaging. Deep learning models based on clinical features, laboratory features, conventional imaging features (infarct volume, number of infarctions), and deep neuroimaging features were trained to predict functional outcomes at 3 months poststroke. Unfavorable outcome was defined as modified Rankin Scale score of 3 or higher at 3 months. The models were evaluated by comparing the area under the receiver operating characteristic curve (AUC).

RESULTS

A model based solely on 14 deep neuroimaging features from CNNs achieved an extremely high AUC of 0.975 (95% confidence interval [CI] = 0.934-0.997) and significantly outperformed the model combining clinical, laboratory, and conventional imaging features (0.772, 95% CI = 0.691-0.847, p < 0.001) in prediction of functional outcomes. The deep neuroimaging model also demonstrated significant improvement over traditional prognostic scores. In an interpretability analysis, the deep neuroimaging features displayed a significant correlation with age, National Institutes of Health Stroke Scale score, infarct volume, and inflammation factors.

CONCLUSIONS

Deep learning models can successfully extract objective neuroimaging features from the routine radiological data in an automatic manner and aid in predicting the functional outcomes in patients with brainstem infarction at 3 months with very high accuracy.

Injury of the dentatorubrothalamic tract in patients with post-traumatic tremor following mild traumatic brain injury: a case-control study

Post-traumatic movement disorder is one of the sequelae of traumatic brain injury. The dentatorubrothalamic tract (DRTT) is reported to be involved in the control of movement. Therefore, injury of the DRTT can be accompanied by abnormal movements, including ataxia, tremor, or dystonia. We investigated DRTT injuries in 27 patients who showed post-traumatic tremor in at least one of four extremities following mild traumatic brain injury. We classified DRTT injuries based on diffusion tensor tractography parameters and configuration: type A: the DRTT showed narrowing, type B: the DRTT showed partial tearing, and type C: the DRTT showed discontinuation. Fractional anisotropy and fiber number of the DRTT were significantly decreased in patients compared with the healthy controls. Based on our DRTT injury classification, among the 54 hemispheres of the 27 patients, type A injury occurred in 22 hemispheres (40.7%) of 17 patients, type B injury was present in 15 hemispheres (27.7%) of 10 patients, and type C injury was observed in 8 hemispheres (14.8%) of 6 patients. Our results suggest that diffusion tensor tractography-based evaluation of the DRTT would be useful when determining cause of post-traumatic tremor in patients with mild traumatic brain injury. The study protocol was approved by the Institutional Review Board of Yeungnam University Hospital (YUMC-2018-09-007) on September 5, 2018.

Aggravation of an injured dentato-rubro-thalamic tract in a patient with mild traumatic brain injury: A case report

RATIONALE

We report on a patient with mild traumatic brain injury (TBI) by follow-up diffusion tensor tractography (DTT), and observed for approximately nine monthsby serial diffusion tensor tractography (DTT).

PATIENT CONCERNS

A 66-year-old male patient was injured in a car crash. Approximately four weeks after the crash, he developed a tremor in the right hand and leg. His symptoms worsened over time.

DIAGNOSES

Approximately six months after the crash, he developed a mild tremor in the left hand. Nine months after the crash, he manifested severe tremor in his right hand, mild resting and intentional tremor in his left hand and both legs, and mild trunkal ataxia.

INTERVENTIONS

N/A.

OUTCOMES

On 3-week DTT, well reconstructed DRTTs were observed in both hemispheres, except for the thinned lower portion of the right DRTT. On 9-month DTT, the right lower DRTT had thinned compared with the 3-week DTT and showed a disruption at the upper portion. The left DRTT showed thinning in the lower portion and tearing in the upper portion compared with 3-week DTT.

LESSONS

Aggravation of an injured DRTT was demonstrated in a patient with mild TBI, using serial DTT examination.

Injury of the dentato-rubro-thalamic tract in patients with cerebellar infarct: Case report

RATIONALE

Several studies using diffusion tensor tractography (DTT) have reported on injury in the dentato-rubro-thalamic tract (DRTT) in patients with brain injury. However, there is no study of injury in the DRTT following cerebellar infarct. We report on patients with injury in the DRTT following cerebellar infarct, demonstrated on DTT.

PATIENT CONCERNS

Three patients with cerebellar infarct were enrolled in this study. Diffusion tensor imaging data were acquired at 3 weeks (patient 1) and 2 weeks (patients 2 and 3) after onset and the DRTT was reconstructed. The Scale for Assessment and Rating of Ataxiaand the Functional Ambulation Category were used for evaluation of ataxia and gait function.

DIAGNOSES AND OUTCOMES

With clinical evaluation, patient 1 scored 18, patient 2 scored 22, and patient 3 scored 28 points on the Scale for Assessment and Rating of Ataxia. On the Functional Ambulation Category patient 1 scored 2, patient 2 scored 2, and patient 3 scored 1 point. DRTT abnormalities were as follows: discontinuation (the upper portion of the left DRTT in the patient 1), narrowing (the lower portion of the left DRTT in patient 2, and the whole right DRTT in the patient 3), and nonreconstruction (the left DRTT in the patient 3).

LESSONS

Using DTT, we demonstrated injury in the DRTT in 3 patients with severe ataxia following cerebellar infarct. We believe that evaluation of the DRTT would be helpful in patients who develop ataxia following cerebellar infarct.

Severe ataxia due to injuries of neural tract detected by diffusion tensor tractography in a patient with pontine hemorrhage: A case report

RATIONALE

We examined injuries of the dentato-rubro-thalamic tract (DRTT), cortico-ponto-cerebellar tract (CPCT), dorsal spinocerebellar tract (SCT), and inferior cerebellar peduncle (ICP) in a patient with severe ataxia following bilateral tegmental pontine hemorrhage (PH), using diffusion tensor tractography (DTT).

PATIENT CONCERNS

A 75-year-old female patient underwent conservative management for bilateral tegmental PH. She presented with moderate motor weakness, severe resting and intentional tremor on both hands, and severe truncal ataxia (Scale for Assessment and Rating of Ataxia [25 points/0-40 points: a higher score indicates a worse state]), and she was not able to sit independently.

DIAGNOSES AND OUTCOMES

On DTT taken at 2 weeks after initial presentation, both DRTTs and the left dorsal SCT were not reconstructed, whereas the CPCTs showed thinning of the entire pathways between the primary sensorimotor cortex and cerebellum in both hemispheres. The right ICP was discontinued at the transverse cerebellar branch of the ICP and thinning of the left ICP was observed in the vertical and transverse cerebellar branch of the ICP.

LESSONS

Using DTT, concurrent injuries of the DRTT, CPCT, dorsal SCT, and ICP were demonstrated in a patient with severe ataxia following PH. Our result suggests the necessity of evaluation of these neural tracts in patients who develop ataxia after brain injury.

Depiction of dentatorubrothalamic tract fibers in patients with Parkinson's disease and multiple sclerosis in deep brain stimulation

BACKGROUND

We wanted to depict fibers of the dentatorubrothalamic tract in patients with Parkinson's disease and multiple sclerosis in order to use this knowledge for clinical routine and to show its relation to the corticospinal tract for deep brain stimulation. Fibers of these white matter tracts were depicted between February 2014 and February 2015 in nine patients of all ages. There were seven men and two women. The mean age was 60 years. We used a 3DT1 sequence for the navigation. Additional scanning time was less than 9 min. Both tracts were portrayed in all patients.

RESULTS

We were able to successfully portray these white matter tracts in all patients. We visualized the medial and lateral parts of the corticospinal tract by using a region of interest which covered the whole motor cortex. Furthermore we segmented the motor cortex. The fibers ran from this area of the brain through the internal capsule and they could be followed until their entry in the brainstem. The dentatorubrothalamic tract was smaller than the corticospinal tract. It was situated medio-posteriorly of the corticospinal tract. After decussation to the contralateral red nucleus it was localised next to the midline when it entered the motor cortex. From the thalamus on, it proceeds medially and posteriorly of the corticospinal tract further to the motor cortex. Depiction of the whole tract is essential for the differentiation of the dentatorubrothalamic tract with the corticospinal tract.

CONCLUSIONS

The depiction of the dentatorubrothalamic tract might be useful for neurosurgeons when deep brain stimulation is planned. Knowing its relation to other white matter tracts can help physicians like neurosurgeons or neurologists avoid side effects and deal with patients with DBS. The position of the electrode might be crucial for a satisfactory outcome.

Injury of the dentato-rubro-thalamic tract in a patient with mild traumatic brain injury

BACKGROUND

Several studies using diffusion tensor tractography (DTT) have demonstrated injury of the dentato-rubro-thalamic tract (DRTT) in various brain pathologies. However, no study on traumatic brain injury (TBI) has been reported. This case study attempted to demonstrate injury of the DRTT in a patient with mild TBI, using DTT.

CASE DESCRIPTION

A 41-year-old female patient suffered from head trauma resulting from flexion-hyperextension injury by being hit from behind by a running car while stopped at an intersection. The patient lost consciousness and experienced post-traumatic amnesia for ∼1minute from the time of the car-accident. The patient's Glasgow Coma Scale score was 15. No specific lesion was observed on brain MRI. At 2 weeks after onset, the patient began to show resting and intentional tremor (more severe in the right upper and lower extremities) and ataxic gait. Her symptoms had been aggravated with the passage of time. On 1-month DTT, the left DRTT, which originated from the left dentate nucleus of the cerebellum, was thinner than the right DRTT.

CONCLUSIONS

This study demonstrated injury of the DRTT in a patient with tremor and ataxia following mild TBI, using DTT. It is believed that analysis of the DRTT using DTT would be useful in elucidating the cause of post-traumatic abnormal movements.

Ataxia and tremor due to lesions involving cerebellar projection pathways: a DTI tractographic study in six patients

Focal lesions of brainstem, thalamus, and subcortical white matter may cause movement disorders that are clinically indistinguishable from cerebellar symptoms. It is suspected that ataxia in these cases is due to damage of efferent or afferent pathways of the cerebellum. However, the precise anatomical correlate often remains undefined. We used deterministic diffusion tensor magnetic resonance imaging (DTI) tractography to study the anatomical relationship between lesions causing ataxia and efferent cerebellar pathways. Study subjects were six male patients with focal lesions of different etiology (demyelination, hemorrhage, ischemia, neoplasm) outside the cerebellum. Five patients had cerebellar-like ataxia with prominent contralateral upper limb involvement. One patient with an almost midline mesencephalic lesion had a symmetrical ataxic syndrome. We used 3T MRI (Intera, Philips Medical Systems, Best, Netherlands) and DTI tractography (32 directions, StealthViz DTI, Medtronic Navigation, Louisville, USA) to delineate the dentato-rubro-thalamo-cortical tract (DRT). In all patients, tractography demonstrated focal lesions affecting the DRT in different locations. We conclude that in vivo mapping of cerebral pathways using DTI tractography in patients with focal extracerebellar brain lesions may provide direct evidence of circumscribed damage to the DRT, causing unilateral cerebellar-like ataxia. Also, a unilateral mesencephalic lesion at the level of the crossing of the DRT may cause bilateral ataxia.

Time-dependent structural changes of the dentatothalamic pathway in children treated for posterior fossa tumor

BACKGROUND AND PURPOSE

Injury to the dentatothalamic pathway that originates in the cerebellum has been suggested as a mechanism for neurologic complications in children treated for posterior fossa tumors. We hypothesized that time-dependent changes occur in the dentatothalamic pathway.

MATERIALS AND METHODS

Diffusion tensor evaluation was performed in 14 children (median age, 4.1 years; age range, 1-20 years) who underwent serial MR imaging at 3T as part of routine follow-up after posterior fossa tumor resection with or without adjuvant therapy. Tensor metrics were obtained in the acute (≤1 week), subacute (1 to <6 months), and chronic (≥6 months) periods after surgery. We evaluated the following dentatothalamic constituents: bilateral dentate nuclei, cerebellar white matter, and superior cerebellar peduncles. Serial dentate nuclei volumes were also obtained and compared with the patient's baseline.

RESULTS

The most significant tensor changes to the superior cerebellar peduncles and cerebellar white matter occurred in the subacute period, regardless of the tumor pathology or therapy regimen, with signs of recovery in the chronic period. However, chronic volume loss and reduced mean diffusivity were observed in the dentate nuclei and did not reverse. This atrophy was associated with radiation therapy and symptoms of ataxia.

CONCLUSIONS

Longitudinal diffusion MR imaging in children treated for posterior fossa tumors showed time-dependent tensor changes in components of the dentatothalamic pathway that suggest evolution of structural damage with inflammation and recovery of tissue directionality. However, the dentate nuclei did not show tensor or volumetric recovery, suggesting that the injury may be chronic.

Spinocerebellar ataxia types 1, 2, 3 and 6: the clinical spectrum of ataxia and morphometric brainstem and cerebellar findings

To assess the clinical spectrum of ataxia and cerebellar oculomotor deficits in the most common spinocerebellar ataxias (SCAs), we analysed the baseline data of the EUROSCA natural history study, a multicentric cohort study of 526 patients with either spinocerebellar ataxia type 1, 2, 3 or 6. To quantify ataxia symptoms, we used the Scale for the Assessment and Rating of Ataxia (SARA). The presence of cerebellar oculomotor signs was assessed using the Inventory of Non-Ataxia Symptoms (INAS). In a subgroup of patients, in which magnetic resonance images (MRIs) were available, we correlated MRI morphometric measures with clinical signs on an exploratory basis. The SARA subscores posture and gait (items 1-3), speech (item 4) and the limb kinetic subscore (items 5-8) did not differ between the genotypes. The scores of SARA item 3 (sitting), 5 (finger chase) and 6 (nose-finger test) differed between the subtypes whereas the scores of the remaining items were not different. In SCA1, ataxia symptoms were correlated with brainstem atrophy and in SCA3 with both brainstem and cerebellar atrophy. Cerebellar oculomotor deficits were most frequent in SCA6 followed by SCA3, whereas these abnormalities were less frequent in SCA1 and SCA2. Our data suggest that vestibulocerebellar, spinocerebellar and pontocerebellar circuits in SCA1, SCA2, SCA3 and SCA6 are functionally impaired to almost the same degree, but at different anatomical levels. The seemingly low prevalence of cerebellar oculomotor deficits in SCA1 and SCA2 is most probably related to the defective saccadic system in these disorders.

Hemi- and monoataxia in cerebellar hemispheres and peduncles stroke lesions: topographical correlations

Limb ataxia of sudden onset is due to a vascular lesion in either the cerebellum or the brainstem (posterior circulation, PC, territory). This sign can involve both the upper and the lower limb (hemiataxia) or only one limb (monoataxia). The topographical correlates of limb ataxia have been studied only in brainstem strokes. Therefore, it is not yet known whether this sign is useful to localize the lesion within the entire cerebellar system, both the cerebellar hemisphere and the cerebellar brainstem pathways. Limb ataxia was semi-quantified according to the International Cooperative Ataxia Rating Scale in 92 consecutive patients with acute PC stroke. Limb ataxia was present in 70 patients. Four topographical patterns based on magnetic resonance imaging findings were identified: picaCH pattern (posterior inferior cerebellar artery infarct); scaCH pattern (superior cerebellar artery infarct); CH/CP pattern (infarct involving both the cerebellum and the brainstem cerebellar pathways); and CP pattern (infarct involving the brainstem cerebellar pathways). Hemiataxia was present in (47/70; 67.1%) and monoataxia in (23/70; 32.9%) of patients. Monoataxia involved the upper limb in (19/70; 27.1%) and the lower limb in (4/70; 5.7%) of patients. Limb ataxia usually localized the lesion ipsilaterally (picaCH, scaCH, CH/CP, and CP patterns involving the medulla and sometimes the pons) (53/70; 75.7%), but it might be due also to contralateral (CP pattern involving the pons or midbrain) (16/70; 22.9%) or bilateral lesions (1/70). Limb ataxia usually localizes the lesion ipsilaterally but the infarct might be sometimes contralateral. The occurrence of monoataxia may suggest that the cerebellar system is somatotopically organized.

Ataxia in patients with brain infarcts and hemorrhages

Gait and limb incoordination and ataxia are most often found in patients with brainstem and cerebellar infarcts and hemorrhages. Lesions involving the thalamus and the deep portions of the cerebral hemispheres also may cause ataxia accompanied by weakness and sensory symptoms. Patients who have lesions in the lateral medulla and inferior cerebellum often topple, lean, or veer when attempting to sit, stand, or walk. They list to the side or abruptly veer when walking. The affected limbs are often hypotonic. In pontine lesions, ataxia is accompanied by weakness and pyramidal tract signs as part of an ataxic hemiparesis syndrome. In lesions affecting the superior cerebellum and the brachium conjunctivum, limb dysmetria and overshoot and dysarthria predominate and gait ataxia is absent or slight and transient. Infarcts affecting the thalamus can cause gait instability and astasia with ataxia. Lateral thalamic lesions are characterized by hemisensory symptoms, extrapyramidal limb postures and dysfunction, and gait ataxia. Lesions that affect the posterior limb of the internal capsule and its afferent and efferent projections may also cause an ataxic hemiparesis syndrome, often with accompanying hemisensory abnormalities.

Dentatorubrothalamic tract in human brain: diffusion tensor tractography study

INTRODUCTION

The dentatorubrothalamic tract (DRTT) originates from the dentate nucleus in the cerebellum and terminates in the contralateral ventrolateral nucleus (VL) of the thalamus after decussating to the contralateral red nucleus. Identification of the DRTT is difficult due to the fact that it is a long, multisynaptic, neural tract crossing to the opposite hemisphere. In the current study, we attempted to identify the DRTT in the human brain using a probabilistic tractography technique of diffusion tensor imaging.

METHODS

Diffusion tensor imaging was performed at 1.5-T using a synergy-L sensitivity encoding head coil. DRTTs were obtained by selection of fibers passing through three regions of interest (the dentate nucleus, the superior cerebellar peduncle, and the contralateral red nucleus) from 41 healthy volunteers. Probabilistic mapping was obtained from the highest probabilistic location at 2.3 mm above the anterior commissure-posterior commissure level.

RESULTS

DRTTs of all subjects, which originated from the dentate nucleus, ascended through the junction of the superior cerebellar peduncle and the contralateral red nucleus and then terminated at the VL nucleus of the thalamus. The highest probabilistic location for the DRTT at the thalamus was compatible with the location of the VL nucleus.

CONCLUSIONS

We identified the DRTT in the human brain using probabilistic tractography. Our results could be useful in research on movement control.

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.