The Kernohan-Woltman Notch Phenomenon : A Systematic Review of Clinical and Radiologic Presentation, Surgical Management, and Functional Prognosis

Neuro-oncologic Emergencies

OBJECTIVE

Neuro-oncologic emergencies have become more frequent as cancer remains one of the leading causes of death in the United States, second only to heart disease. This article highlights key aspects of epidemiology, diagnosis, and management of acute neurologic complications in primary central nervous system malignancies and systemic cancer, following three thematic classifications: (1) complications that are anatomically or intrinsically tumor-related, (2) complications that are tumor-mediated, and (3) complications that are treatment-related.

LATEST DEVELOPMENTS

The main driver of mortality in patients with brain metastasis is systemic disease progression; however, intracranial hypertension, treatment-resistant seizures, and overall decline due to increased intracranial burden of disease are the main factors underlying neurologic-related deaths. Advances in the understanding of tumor-specific characteristics can better inform risk stratification of neurologic complications. Following standardized grading and management algorithms for neurotoxic syndromes related to newer immunologic therapies is paramount to achieving favorable outcomes.

ESSENTIAL POINTS

Neuro-oncologic emergencies span the boundaries of subspecialties in neurology and require a broad understanding of neuroimmunology, neuronal hyperexcitability, CSF flow dynamics, intracranial compliance, and neuroanatomy.

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.

Temporal lobe uncal herniation with contralateral superior cerebellar artery infarct

Herniation of the temporal lobe uncus typically leads to the compression of the ipsilateral oculomotor nerve, resulting in ipsilateral mydriasis, as well as compression of the ipsilateral posterior cerebral artery, leading to infarction in the posterior inferior temporal lobe and medial occipital cortex. In this report, we present the case of a 45-year-old man with a large left subdural hematoma. At autopsy, we observed left cingulate and uncal herniations, along with the characteristic lesions of Kernohan notch phenomenon due to compression of the contralateral cerebral peduncle. Additionally, a hemorrhagic infarct was identified in the right cerebellar hemisphere in the distribution of the superior cerebellar artery (SCA). This case provides the first autopsy report of uncal herniation with contralateral SCA infarct, an extremely rare condition. Importantly, this vascular complication may often go unnoticed in patients with Kernohan notch phenomenon although it may carry a grave clinical prognosis.

Kernohan-Woltman Notch Phenomenon Following Acute Subdural Hematoma

A 72-year-old right-handed female patient was operated on for left-sided acute subdural hematoma responsible for coma. Two weeks afterward, her neurological status had improved with a Glasgow Coma Scale score of 14 and a paradoxical left-sided hemiparesis. The brain magnetic resonance imaging displayed a diffusion-restricting, hyper fluid-attenuated inversion recovery lesion of the right cerebral peduncle facing the tentorial notch, and the patient was diagnosed with Kernohan-Woltman notch phenomenon. This allowed to focus the neurological rehabiliation on the ipsilateral motor deficit as well as the hemineglect.

Degree of basal cisterns compression predicting mortality and functional outcome after craniotomy and primary decompressive craniectomy in acute subdural hematoma population

OBJECTIVES

The compression of basal cisterns on CT is one of the signs of intracranial hypertension in TBI population. This study evaluates the relationship between the degree of basal cisterns effacement and outcomes in aSDH population.

METHODS

The study includes prospectively collected data from 290 patients who underwent osteoplastic craniotomy (OC) or primary decompressive craniectomy (pDC) for aSDH from 2016 to 2021. Univariate and multivariate regression analyses were performed to evaluate the association of baseline characteristics and extent of basal cisterns compression on pre-operative and post-operative CT scans with the outcomes at the time of discharge. Outcomes were dichotomized into mortality (and unfavourable (GOS 1-3 vs GOS 4-5). The degree of cisternal compression was evaluated using the cisternal effacement score of perimesencephalic and quadrigeminal cisternal components. Critical thresholds associated with the outcomes were calculated.

RESULTS

Age and pre-/post-operative degree of cisternal compression were the strongest independent predictors of intrahospital mortality in a whole sample and separately in OC and pDC subgroups. The unfavourable outcome was independently predicted by age, pre-/post-operative status of cisternal compression and initial GCS. Critical thresholds associated with the mortality and poor functional outcome were, respectively, age ≥ 70 (OR 3.14 [CI 95% 1.82-5.46], p < 0.001) and ≥ 67 (OR 3.87 [CI 95% 2.33-6.54], p < 0.001), pre-operative cisternal effacement score ≥ 9 (OR 6.39 [CI 95% 3.62-11.53], p < 0.001) and ≥ 7 (OR 4.93 [CI 95% 2.96-8.38], p < 0.001), post-operative cisternal effacement score ≥ 6 (OR 20.6 [CI 95% 10.08-45.10], p < 0.001) and ≥ 3 (OR 7.47 [CI 95% 3.87-15.73], p < 0.001) and initial GCS ≤ 8 (OR 0.24 [CI 95% 0.13-0.43], p < 0.001 and OR 0.12 [CI 95% 0.07-0.21], p < 0.001).

CONCLUSIONS

After adjusting for baseline characteristics, age and degree of cisternal compression remained the independent predictors of mortality, whereas unfavourable outcomes were associated with age, cisternal obliteration and GCS on presentation.

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.

Prognostic Factors of Mortality and Functional Outcome for Acute Subdural Hematoma: A Review Article

Acute subdural hematoma (ASDH) is the most frequent intracranial traumatic lesion requiring surgery in high-income countries. To date, uncertainty remains regarding the odds of mortality or functional outcome of patients with ASDH, regardless of whether they are operated on. This review aims to shed light on the clinical and radiologic factors associated with ASDH outcome. A scoping review was conducted on Medline database from inception to 2023. This review yielded 41 patient series. In the general population, specific clinical (admission Glasgow Coma Scale [GCS], abnormal pupil exam, time to surgery, decompressive craniectomy, raised postoperative intracranial pressure) and radiologic (ASDH thickness, midline shift, thickness/midline shift ratio, uncal herniation, and brain density difference) factors were associated with mortality (grade III). Other clinical (admission GCS, decompressive craniectomy) and radiologic (ASDH volume, thickness/midline shift ratio, uncal herniation, loss of basal cisterns, petechiae, and brain density difference) factors were associated with functional outcome (grade III). In the elderly, only postoperative GCS and midline shift on brain computed tomography were associated with mortality (grade III). Comorbidities, abnormal pupil examination, postoperative GCS, intensive care unit hospitalization, and midline shift were associated with functional outcome (grade III). Based on these factors, the SHE (Subdural Hematoma in the Elderly) and the RASH (Richmond Acute Subdural Hematoma) scores could be used in daily clinical practice. This review has underlined a few supplementary factors of prognostic interest in patients with ASDH, and highlighted two predictive scores that could be used in clinical practice to guide and assist clinicians in surgical indication.

Duret Brainstem Hemorrhage After Transtentorial Descending Brain Herniation: A Systematic Review and Meta-Analysis

BACKGROUND

Historically, the occurrence of hemorrhage in the brainstem after an episode of supratentorial intracranial hypertension was described by Henri Duret in 1878. Nevertheless, to date the eponym Duret brainstem hemorrhage (DBH) lacks systematic evidence regarding its epidemiology, pathophysiology, clinical and radiologic presentation, and outcome.

METHODS

We conducted a systematic literature review and meta-analysis using the Medline database from inception to 2022 looking for English-language articles concerning DBH, in accordance with the PRISMA guidelines.

RESULTS

The research yielded 28 articles for 32 patients (mean age, 50 years; male/female ratio, 3:1). Of patients, 41% had head trauma causing 63% of subdural hematoma, responsible for coma in 78% and mydriasis in 69%. DBH appeared on the emergency imaging in 41% and on delayed imaging in 56%. DBH was located in the midbrain in 41% of the patients, and in the upper middle pons in 56%. DBH was caused by sudden downward displacement of the upper brainstem secondary to supratentorial intracranial hypertension (91%), intracranial hypotension (6%), or mechanical traction (3%). Such downward displacement caused the rupture of basilar artery perforators. Brainstem focal symptoms (P = 0.003) and decompressive craniectomy (P = 0.164) were potential favorable prognostic factors, whereas an age >50 years showed a trend toward a poor prognosis (P = 0.0731).

CONCLUSIONS

Unlike its historical description, DBH appears as a focal hematoma in the upper brainstem caused by the rupture of anteromedial basilar artery perforators after sudden downward displacement of the brainstem, regardless of its cause.

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.