Ipsilateral hemiparesis: the forgotten history of this paradoxical neurological sign

Syndrome of the third frontal convolution: Léon Ectors´ legacy on paradoxical ipsilateral hemiparesis

Since the crossed control of sensitive-motor body functions by the contralateral cerebral hemispheres was recognized in the early 18th century, clinicians have been baffled by patients developing a motor deficit involving the extremities on the same side as an intracranial lesion. In the first third of the 20th century, three main hypotheses were proposed to explain this so-called ipsilateral or paradoxical hemiparesis: (1) the absence of decussation of the corticospinal tracts; (2) diaschisis, or blocking of the normal input to a brain region anatomically distant from the injured site; and (3) compression of the contralateral cerebral peduncle against the tentorial border, also known as the Kernohan-Woltman notch phenomenon. Here, we deal with the less widely known contributions of the Belgian neurosurgeon Léon Ectors, who included this paradoxical deficit within a neurological syndrome he considered highly specific for an early diagnosis of those meningiomas growing over the third frontal convolution. The present manuscript includes a systematic review of the cases of ipsilateral hemiparesis secondary to intracranial masses reported in ancient and modern scientific medical literature. We also address in-depth the physiopathological theories accounting for this syndrome and contrast them with Léon Ectors' observations.

The Kinetics of Transtentorial Brain Herniation: Kernohan-Woltman Notch Phenomenon Revisited

PURPOSE OF REVIEW

To critically review recent literature in understanding the pathological consequences of transtentorial brain herniation resulting from unilateral expanding supratentorial mass lesions.

RECENT FINDINGS

Modern neuroimaging assists in understanding the consequences of transtentorial brain herniation with the development of the Kernohan-Woltman notch phenomenon. MRI studies in post-operative patients undergoing craniotomy and removal of expanding unilateral hemispheric mass lesions (usually an extradural or subdural hematoma) have shown striking findings in the contralateral crus cerebri suggestive of damage as a result of impact against the free margin of the opposite tentorium as suggested by Kernohan and Woltman nearly a century back in autopsy studies. MR changes include T1 hypointensity, T2 and fluid-attenuated inversion recovery (FLAIR) hyperintensity, DW1 hyperintensity with restriction of diffusion, presence of hypointensity in GRE sequences and evidence of axonal damage in the corticospinal tracts in the cerebral peduncle in diffusion tensor imaging and MR tractography. The pathological basis of such changes may be variable or a combination of several pathological processes, which may all be related to the impact/compression of the contralateral crus with the tentorial margin. These include contusion, compression, demyelination, and perhaps most importantly microvascular damage including microbleeds. The role of uncal herniation is debatable. It appears that as a result of massive lateral shift in the supratentorial compartment, there is a transient forceful impact of the opposite cerebral peduncle against the rigid tentorial border to induce one or more of the abovementioned phenomena to explain the imaging findings. The limitation of these studies is that most of them have been done in the post-operative periods and surgical manipulations can surely alter anatomical relationships between intracranial structures. The exact sequence of events happening intracranially in the face of rapidly expanding supratentorial mass lesions is largely unknown. Even with rapid progress in neuroimaging, documentation of such changes during life are difficult, principally for logistic reasons. Consequently, the very truth of the much taught about phenomenon of uncal herniation and the resultant Kernohan-Woltman notch phenomenon and the false localizing sign of unilateral motor weakness and contralateral pupillary dilation have been questioned. Animal experimentation and autopsy studies have not contributed much in our understanding of the actual process happening intracranially in such an emergent situation. The midbrain undoubtedly is the key structure bearing the brunt of the effect of brain shift which is more lateral than downward in cases with unilateral expanding lesions. Structural changes in the cerebral peduncles have now been visualized with modern neuroimaging. These alterations may result from the interplay of one or more factors which include compression, contusion, demyelination, and perhaps most importantly microvascular ischemia and hemorrhage resulting from a forceful yet transient impact of the cerebral peduncle with the tough tentorial margin. The last mentioned hypothesis would be in conformity with Kernohan and Woltman's concept of elastic deformation of the midbrain. In the present article an attempt is made to provide a historical account of the changing concepts in relation to brain herniation as systematically and chronologically as possible, and then, critically review recent neuroimaging observations with a view to hypothesize on the sequence of events during transtentorial brain herniation.

Beyond uncal herniation: An updated diagnostic reappraisal of ipsilateral hemiparesis and the Kernohan-Woltman notch phenomenon

PURPOSE

This works comprehensively analyses a modern cohort of patients with ipsilateral hemiparesis (IH) and discusses the pathophysiological theories elaborated to explain this paradoxical neurological sign according to the findings from contemporary neuroimaging and neurophysiological techniques.

METHODS

A descriptive analysis of the epidemiological, clinical, neuroradiological, neurophysiological, and outcome data in a series of 102 case reports of IH published on since the introduction of CT/MRI diagnostic methods (years 1977-2021) was performed.

RESULTS

IH mostly developed acutely (75.8%) after traumatic brain injury (50%), as a consequence of the encephalic distortions exerted by an intracranial haemorrhage eventually causing contralateral peduncle compression. Sixty-one patients developed a structural lesion involving the contralateral cerebral peduncle (SLCP) demonstrated by modern imaging tools. This SLCP showed certain variability in its morphology and topography, but it seems pathologically consistent with the lesion originally described in 1929 by Kernohan & Woltman. The study of motor evoked potentials was seldom employed for the diagnosis of IH. Most patients underwent surgical decompression, and a 69.1% experienced some improvement of the motor deficit.

CONCLUSIONS

Modern diagnostic methods support that most cases in the present series developed IH following the KWNP model. The SLCP is presumably the consequence of either compression or contusion of the cerebral peduncle against the tentorial border, although focal arterial ischemia may also play a contributing role. Some improvement of the motor deficit should be expected even in the presence of a SLCP, provided the axons of the CST were not completely severed.

Kernohan-Woltman notch phenomenon in patient with subdural hematoma and ipsilateral hemiparesis in Bukavu

Key Clinical Message

Kernohan-Woltman phenomenon is a rare and paradoxical neurological situation in which a transtentorial lesion leads to compression of the contralateral cerebral peduncle responsible for compression of the descending corticospinal fibers with clinical consequence of a motor deficit ipsilateral to the primary lesion. This phenomenon should attract the attention of clinicians in order to avoid unfortunate incidents such as wrong-side craniotomy in neurosurgical practice. In this work, we report a similar situation.

Abstract

The Kernohan-Woltman notch phenomenon is a rare and paradoxical neurological situation in which transtentorial damage is observed leading to compression of the contralateral cerebral peduncle responsible for compression of descending corticospinal fibers with the clinical consequence of a motor deficit ipsilateral to the primary lesion. This phenomenon has been found in several situations including tumors and cerebral hematomas after craniocerebral trauma. In this work, we have reported the case of a 52-year-old man with hemiparesis ipsilateral to a large chronic subdural hematoma.

Ipsilateral Hemiparesis in a Patient With Existing Contralateral Hemiparesis: A Case Report of a Rare Presentation of Ischemic Stroke

Supratentorial strokes causing ipsilateral hemiparesis (ILH) are rare. We report a middle-aged male with multiple atherosclerotic risk factors, who had previously suffered a right-hemispheric stroke that caused left hemiplegia. Subsequently, he presented with worsening left-sided hemiplegia, with imaging revealing a left-hemispheric stroke. Diffusion tensor tract imaging showed crossed motor tracts, with disruption of the left-sided pyramidal tract. During his stay, he developed right hemiplegia due to the expansion of the same left-hemispheric infarct. Potential mechanisms for ILH in a stroke include injury to reorganized tracts following an initial insult and congenitally uncrossed motor tracts. In our patient, after his first stroke, the left hemisphere likely assumed greater ipsilateral motor control, causing ILH after the recent stroke. Our case adds to the literature on this interesting phenomenon and provides further insight into post-stroke recovery.

Paradoxical contralateral hemiparesis in spontaneous spinal epidural hematoma: a case report

BACKGROUND

Hemiparesis associated with spontaneous spinal epidural hematoma (SSEH) usually occurs ipsilateral to the hematoma. We here report the case of a patient with paradoxical hemiparesis contralateral to a spinal lesion due to SSEH.

CASE PRESENTATION

A 70-year-old woman was identified in routine clinical practice; she presented with acute-onset neck pain and left hemiparesis. Neurological examination showed left-sided sensory-motor hemiparesis without facial involvement. Cervical MRI showed a dorsolateral epidural hematoma compressing the spinal cord at the C2 to C3 level. Axial imaging demonstrated a crescent hematoma on the right side, which is contralateral to the hemiparesis, and lateral displacement of the spinal cord. Spinal angiography revealed no abnormal vessels. Based on clinical presentation and MRI findings, a diagnosis of SSEH was made. The patient was managed conservatively. The symptoms completely resolved without any neurological deficits, and the hematoma disappeared on the follow-up MRI.

CONCLUSIONS

Paradoxical contralateral hemiparesis is one of the possible presenting symptoms in patients with SSEH. This case demonstrates the existence of the paradoxical contralateral hemiparesis associated with spinal compressive lesions. A plausible mechanism of the phenomenon is discussed.

Spontaneous intracranial hypotension complicated by unilateral subdural hematoma, coma, and the rare Kernohan's notch phenomenon

Spontaneous intracranial hypotension (SIH) is a highly underdiagnosed condition with a wide range of manifestations. Although SIH has traditionally been viewed as having a benign disease course, recent evidence suggests otherwise. In this case report, we present a 71-year-old woman who was previously treated with a tapered dose of corticosteroids for an episode of SIH with behavioral manifestations. In this current report, we present her second episode which was complicated by a unilateral sub-acute subdural hematoma leading to loss of consciousness and coma. While the patient regained full consciousness and recovered considerably, she still suffers from ipsilateral hemiparesis as a result of Kernohan's notch phenomenon 2 years post-hospitalization. To the author's knowledge, this is the first case to involve persistent motor deficit after the resolution of SIH. We believe that surgical hematoma evacuation prior to addressing the cerebrospinal fluid leak may have contributed to aggregated downward displacement of the brain precipitating Kernohan's notch phenomenon.

Kernohan-Woltman notch phenomenon: an exceptional neurological picture?

INTRODUCTION

Ipsilateral hemiparesis (IH) can be defined as a paradoxical dysfunction of the first motor neuron involving the extremities on the opposite side to that expected, given the location of the triggering intracranial pathology. Compression of the corticospinal tract (CSt) along its course through the contralateral cerebral peduncle against the free edge of the tentorium, known as the Kernohan-Woltman notch phenomenon (KWNP), represents the main cause of IH.

METHODS

This retrospective study analyses a series of 12 patients diagnosed with IH secondary to KWNP treated at our institution, including a descriptive study of epidemiological, clinical, radiological, neurophysiological, and prognostic variables.

RESULTS

In 75% of the cases, symptoms had an acute or subacute onset. Initial imaging studies showed signs of significant mass effect in half of the patients, whereas magnetic resonance imaging (MRI) identified a structural lesion in the contralateral cerebral peduncle in two thirds of them. Impairment of the motor evoked potentials (MEP) was verified in 4 patients. During follow-up 7 patients experienced improvement in motor activity, and near half of the cases were classified in the first three categories of the modified Rankin scale.

CONCLUSIONS

In contrast to prior historical series, most of our patients developed a KWNP secondary to a traumatic mechanism. MRI represents the optimal method to identify both the classic cerebral peduncle notch and the underlying structural lesion of the CSt. The use of MEP can help to establish the diagnosis, especially in those cases lacking definite radiological findings.

A case of Kernohan-Woltman notch phenomenon caused by an epidural hematoma: the diagnostic and prognostic value of PET/CT imaging

Background

Kernohan-Woltman notch phenomenon (KWNP) classically occurs when a lesion causes compression of the contralateral cerebral peduncle against the tentorium, resulting in ipsilateral hemiparesis. It has been studied clinically, radiologically and electrophysiologically which all confirmed to cause false localizing motor signs. Here, we demonstrate the potential use of fluorine-18 fluorodeoxyglucose (18 F-FDG) positron emission tomography/computed tomography (PET/CT) to identify KWNP caused by an epidural hematoma.

Case presentation

A 29-year-old male patient post right-sided traumatic brain injury presenting with persistent ipsilateral hemiparesis. Patient underwent decompressive craniotomy and intracranial hematoma evacuation. Brain magnetic resonance imaging in the postoperative period showed a subtle lesion in the left cerebral peduncle. PET/CT was performed to exclude early brain tumor and explain his ipsilateral hemiparesis. PET/CT imaging demonstrated a focal region of intense 18 F-FDG uptake in the left cerebral peduncle. Throughout the treatment in outpatient neurorehabilitation unit, the patient exhibited a gradual recovery of his right hemiparesis.

Conclusion

In our case report, for the first time, PET/CT offered microstructural and functional confirmation of KWNP. Moreover, our case suggests that 18 F-FDG PET/CT may serve as an important reference for the probability of functional recovery.

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.

Usefulness of Diffusion Tensor Imaging in Unexplained Ipsilateral Hemiplegia

Ipsilateral hemiparesis is a rare and challenging sign in clinical neurological practice. Although the etiology of this manifestation is poorly understood, recent studies have attempted to probe the pathomechanism of this sign with advanced radiological techniques. Additional knowledge about the lesion and unraveling the pathomechanisms causing neurological impairments are important to predict the prognosis and clinical course and to aid in rehabilitation. Therefore, we present a case of a patient with a traumatic subdural hematoma on the left hemisphere and left spastic hemiparesis. Using diffusion tensor imaging (DTI), we concluded that the right corticospinal tract injury caused by compression of the cerebral peduncle accounted for the ipsilateral hemiparesis, also known as Kernohan's notch phenomenon. Thus, this case report highlights the usefulness of the newer radiological techniques, such as DTI, to identify the pathomechanisms of neurological presentations.

Unilateral cerebral herniation resulting in combined contralateral superior cerebellar artery territory infarction and mesencephalic injury: Two cases of a severe unrecognized variant of Kernohan notch phenomenon?

A case of unilateral cerebral herniation due to an acute middle cerebral artery territory infarct and a second case of unilateral cerebral herniation due to an acute subdural hematoma are presented in this article. In both instances, the unilateral cerebral herniation resulted in a combined contralateral superior cerebellar artery territory infarction and mesencephalic injury. Unilateral cerebral herniation resulting in a combined contralateral superior cerebellar artery territory infarct and mesencephalic injury is previously undescribed in the literature and likely reflects a severe unrecognized variant of Kernohan notch phenomenon.