A rare case of ispilateral hemiparesis in a patient with uncrossed pyramidal tract shown by tractography

This article presents a unique case of ipsilateral hemiparesis in a 66-year-old individual, contrary to the conventional understanding of supratentorial strokes causing contralateral neurological deficits. The patient exhibited persistent weakness and sensory abnormalities on the left side of the body following a left occipital infarct. Neuroimaging revealed a chronic stroke in the left occipital lobe, with diffusion tensor imaging demonstrating uncrossed pyramidal tracts at the level of the medulla. The discussion encompasses the anatomical basis of corticospinal tract crossing, historical perspectives, and previous documented cases of ipsilateral strokes. The rarity of complete uncrossed corticospinal tracts without underlying congenital abnormalities or genetic disorders is highlighted. The study underscores the importance of considering such atypical presentations in stroke evaluations and the role of advanced imaging techniques in confirming diagnosis and understanding underlying mechanisms.

Adaptation in the spinal cord after stroke: Implications for restoring cortical control over the final common pathway

Control of voluntary movement is predicated on integration between circuits in the brain and spinal cord. Although damage is often restricted to supraspinal or spinal circuits in cases of neurological injury, both spinal motor neurons and axons linking these cells to the cortical origins of descending motor commands begin showing changes soon after the brain is injured by stroke. The concept of 'transneuronal degeneration' is not new and has been documented in histological, imaging and electrophysiological studies dating back over a century. Taken together, evidence from these studies agrees more with a system attempting to survive rather than one passively surrendering to degeneration. There tends to be at least some preservation of fibres at the brainstem origin and along the spinal course of the descending white matter tracts, even in severe cases. Myelin-associated proteins are observed in the spinal cord years after stroke onset. Spinal motor neurons remain morphometrically unaltered. Skeletal muscle fibres once innervated by neurons that lose their source of trophic input receive collaterals from adjacent neurons, causing spinal motor units to consolidate and increase in size. Although some level of excitability within the distributed brain network mediating voluntary movement is needed to facilitate recovery, minimal structural connectivity between cortical and spinal motor neurons can support meaningful distal limb function. Restoring access to the final common pathway via the descending input that remains in the spinal cord therefore represents a viable target for directed plasticity, particularly in light of recent advances in rehabilitation medicine.

Motor Evoked Potential Warning Criteria in Supratentorial Surgery: A Scoping Review

During intraoperative monitoring of motor evoked potentials (MEP), heterogeneity across studies in terms of study populations, intraoperative settings, applied warning criteria, and outcome reporting exists. A scoping review of MEP warning criteria in supratentorial surgery was conducted in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR). Sixty-eight studies fulfilled the eligibility criteria. The most commonly used alarm criteria were MEP signal loss, which was always a major warning sign, followed by amplitude reduction and threshold elevation. Irreversible MEP alterations were associated with a higher number of transient and persisting motor deficits compared with the reversible changes. In almost all studies, specificity and Negative Predictive Value (NPV) were high, while in most of them, sensitivity and Positive Predictive Value (PPV) were rather low or modest. Thus, the absence of an irreversible alteration may reassure the neurosurgeon that the patient will not suffer a motor deficit in the short-term and long-term follow-up. Further, MEPs perform well as surrogate markers, and reversible MEP deteriorations after successful intervention indicate motor function preservation postoperatively. However, in future studies, a consensus regarding the definitions of MEP alteration, critical duration of alterations, and outcome reporting should be determined.

Uncrossed corticospinal tract in health and genetic disorders: Review, case report, and clinical implications

BACKGROUND AND PURPOSE

Crossing pathologies of the corticospinal tract (CST) are rare and often associated with genetic disorders. However, they can be present in healthy humans and lead to ipsilateral motor deficits when a lesion to motor areas occurs. Here, we review historical and current literature of CST crossing pathologies and present a rare case of asymmetric crossing of the CST.

METHODS

Description of the case and systematic review of the literature were based on the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The PubMed database was searched for peer-reviewed articles in English since 1950. All articles on ipsilateral stroke, uncrossed CST, and associated neurologic disorders were screened. Furthermore, a literature review between the years 1850 and 1980 including articles in other languages, books, opinions, and case studies was conducted.

RESULTS

Only a few descriptions of CST crossing pathologies exist in healthy humans, whereas they seem to be more common in genetic disorders such as horizontal gaze palsy with progressive scoliosis or congenital mirror movements. Our patient presented with aphasia and left-sided hemiparesis. Computed tomographic (CT) scan revealed a perfusion deficit in the left middle cerebral artery territory, which was confirmed by diffusion-weighted magnetic resonance imaging (MRI), so that thrombolysis was administered. Diffusion tensor imaging with fibre tracking revealed an asymmetric CST crossing.

CONCLUSIONS

The knowledge of CST crossing pathologies is essential if a motor deficit occurs ipsilateral to the lesion side. An ipsilateral deficit should not lead to exclusion or delay of therapeutic options in patients with suspected stroke. Here, a combined evaluation of CT perfusion imaging and MRI diffusion imaging may be of advantage.

Uncrossed corticospinal tracts presenting as transient tumor-related symptomatology

Ipsilateral corticospinal innervation is rare. No prior cases have described ipsilateral tumor-associated symptoms as the presentation of an uncrossed corticospinal tract. Herein, we describe a case associated with a left frontal tumor, presenting with transient ipsilateral hemiparesis and aphasia. Due to the fluctuating symptomatology, we suspected a cerebrovascular cause and initially performed a workup for stroke. Ipsilateral motor innervation was discovered with intraoperative monitoring during the resection of the tumor, and confirmed with postoperative diffusion tensor imaging (DTI). Neurosurgeons should be aware of uncrossed motor system, and include it in the differential of ipsilateral deficit in patients with intracranial tumors.

Compensation of Ipsilateral Motor and Sensory Functions by Contralateral Uncrossed Pathway in a Stroke Patient With Half Brain

ABSTRACT

This study reports a case of motor and sensory function recovery after massive left cerebral infarction in a young man, along with preserved function of the injured hemisphere. He received early rehabilitation therapy in a nerval care unit within 1 wk of surgery, and the rehabilitation lasted for more than 3 yrs. When he gradually recovered from coma, his motor, sensory, and speech functions improved significantly. Two years later, he was able to live independently and returned to work. The findings of functional magnetic resonance imaging, diffusion tensor imaging, somatosensory evoked potential, and motor evoked potential confirmed that there was a strong connection between his right brain and the right limbs. Thus, early rehabilitation is a promising approach for restoring motor and sensory function after massive brain injury or extensive brain tissue damage.

Tractography in Neurosurgery: A Systematic Review of Current Applications

The ability to visualize the brain's fiber connections noninvasively in vivo is relatively young compared with other possibilities of functional magnetic resonance imaging. Although many studies showed tractography to be of promising value for neurosurgical care, the implications remain inconclusive. An overview of current applications is presented in this systematic review. A search was conducted for (("tractography" or "fiber tracking" or "fibre tracking") and "neurosurgery") that produced 751 results. We identified 260 relevant articles and added 20 more from other sources. Most publications concerned surgical planning for resection of tumors (n = 193) and vascular lesions (n = 15). Preoperative use of transcranial magnetic stimulation was discussed in 22 of these articles. Tractography in skull base surgery presents a special challenge (n = 29). Fewer publications evaluated traumatic brain injury (TBI) (n = 25) and spontaneous intracranial bleeding (n = 22). Twenty-three articles focused on tractography in pediatric neurosurgery. Most authors found tractography to be a valuable addition in neurosurgical care. The accuracy of the technique has increased over time. There are articles suggesting that tractography improves patient outcome after tumor resection. However, no reliable biomarkers have yet been described. The better rehabilitation potential after TBI and spontaneous intracranial bleeding compared with brain tumors offers an insight into the process of neurorehabilitation. Tractography and diffusion measurements in some studies showed a correlation with patient outcome that might help uncover the neuroanatomical principles of rehabilitation itself. Alternative corticofugal and cortico-cortical networks have been implicated in motor recovery after ischemic stroke, suggesting more complex mechanisms in neurorehabilitation that go beyond current models. Hence tractography may potentially be able to predict clinical deficits and rehabilitation potential, as well as finding possible explanations for neurologic disorders in retrospect. However, large variations of the results indicate a lack of data to establish robust diagnostical concepts at this point. Therefore, in vivo tractography should still be interpreted with caution and by experienced surgeons.