Kernohan's notch phenomenon in chronic subdural hematoma: MRI findings

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.

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.

Spontaneous chronic subdural hematoma as the cause of oculomotor cranial nerve palsy: A narrative review

Acute complete third nerve palsy with pupillary involvement is usually caused by a posterior communicating artery aneurysm (i.e. "the rule of the pupil"). The pupillary fibers run peripherally in the third nerve and are thus susceptible to the external compression. Headache is usually present, and urgent diagnosis and treatment are warranted. Rarely, however, neuroimaging shows other causes of third nerve palsy. In this study, we perform a literature review of spontaneous chronic subdural hematoma that, although rarely, may cause an acute pupil-involving third nerve palsy as a false localizing sign. We review the localizing, nonlocalizing, and false localizing nature of ocular motor cranial nerve palsy in this setting.

Chameleons, red herrings, and false localizing signs in neurocritical care

False localizing signs (FLS) and other misleading neurological signs have long been an intractable aspect of neurocritical care. Because they suggest an incorrect location or etiology of the pathological lesion, they have often led to misdiagnosis and mismanagement of the patient. Here, we reviewed the existing literature to provide an updated, comprehensive descriptive review of these difficult to diagnose signs in neurocritical care. For each sign presented, we discuss the non-false localizing presentation of symptoms, the common FLS or misleading presentation, etiology/pathogenesis of the sign, and diagnosis, as well as any other clinically relevant considerations. Within cranial neuropathies, we cover cranial nerves III, IV, V, VI, VII, VIII, as well as multiple cranial nerve involvement of IX, X, and XII. FLS ophthalmologic symptoms indicate diagnostically challenging neurological deficits, and here we discuss downbeat nystagmus, ping-pong-gaze, one-and-a-half syndrome, and wall-eyed bilateral nuclear ophthalmoplegia (WEBINO). Cranial herniation syndromes are integral to any discussion of FLS and here we cover Kernohan's notch phenomenon, pseudo-Dandy Walker malformation, and uncal herniation. FLS in the spinal cord have also been relatively well documented, but in addition to compressive lesions, we also discuss newer findings in radiculopathy and disc herniation. Finally, pulmonary syndromes may sometimes be overlooked in discussions of neurological signs but are critically important to recognize and manage in neurocritical care, and here we discuss Cheyne-Stokes respiration, cluster breathing, central neurogenic hyperventilation, ataxic breathing, Ondine's curse, and hypercapnia. Though some of these signs may be rare, the framework for diagnosing and treating them must continue to evolve with our growing understanding of their etiology and varied presentations.

Factors influencing the presence of hemiparesis in chronic subdural hematoma

OBJECTIVE

Chronic subdural hematoma (CSDH) has a variety of clinical presentations, including hemiparesis. Hemiparesis is of the utmost importance because it is one of the major indications for surgical intervention and influences outcome. In the current study, the authors intended to identify factors influencing the presence of hemiparesis in CSDH patients and to determine the threshold value of hematoma thickness and midline shift for development of hemiparesis.

METHODS

The authors retrospectively reviewed 325 patients (266 with unilateral and 59 with bilateral hematomas) with CSDH who underwent surgical evacuation, regardless of presence or absence of hemiparesis.

RESULTS

In univariate analysis, hematoma loculation, age, hematoma maximal thickness, and midline shift were significantly associated with hemiparesis. Moreover, patients with unilateral hematomas had a higher rate of hemiparesis than patients with bilateral hematomas. Sex, trauma history, anticoagulant and antiplatelet drug use, presence of comorbidities, Glasgow Coma Scale score, hematoma density characteristics on CT scan, and hematoma signal intensity on T1- and T2-weighted MRI were not associated with hemiparesis. In multivariate analysis, the presence of loculation and hematoma laterality (unilateral vs bilateral) influenced hemiparesis. For unilateral hematomas, maximal hematoma thickness of 19.8 mm and midline shift of 6.4 mm were associated with a 50% probability of hemiparesis. For bilateral hematomas, 29.0 mm of maximal hematoma thickness and 6.8 mm of shift were associated with a 50% probability of hemiparesis.

CONCLUSIONS

Presence of loculations, unilateral hematomas, older patient age, hematoma maximal thickness, and midline shift were associated with a higher rate of hemiparesis in CSDH patients. Moreover, 19.8 mm of hematoma thickness and 6.4 mm of midline shift were associated with a 50% probability of hemiparesis in patients with unilateral hematomas.

Kernohan-Woltman Notch Phenomenon Caused by Acute Traumatic Subdural Haematoma

A 27-year-old man suffered from right hemiparesis after a closed head injury. Computed tomography (CT) revealed a right hemisphere subdural haematoma with midline structure shifted to the left. The CT finding was believed to be mislabeled because the site of haematoma did not correlate with an ipsilateral hemiparesis. Magnetic resonance imaging revealed a right transtentorial uncal herniation and a small lesion within left cerebral peduncle, suggesting Kernohan-Woltman notch phenomenon (KWNP). KWNP has been rarely seen in patients with acute traumatic subdural haemorrhage. Anatomical small maximum tentorial notch width is the possible anatomical factor predisposing our patient to this phenomenon. (Hong Kong j.emerg.med. 2014;21:116-119)

Brainstem Monitoring in the Neurocritical Care Unit: A Rationale for Real-Time, Automated Neurophysiological Monitoring

Patients with severe traumatic brain injury or large intracranial space-occupying lesions (spontaneous cerebral hemorrhage, infarction, or tumor) commonly present to the neurocritical care unit with an altered mental status. Many experience progressive stupor and coma from mass effects and transtentorial brain herniation compromising the ascending arousal (reticular activating) system. Yet, little progress has been made in the practicality of bedside, noninvasive, real-time, automated, neurophysiological brainstem, or cerebral hemispheric monitoring. In this critical review, we discuss the ascending arousal system, brain herniation, and shortcomings of our current management including the neurological exam, intracranial pressure monitoring, and neuroimaging. We present a rationale for the development of nurse-friendly-continuous, automated, and alarmed-evoked potential monitoring, based upon the clinical and experimental literature, advances in the prognostication of cerebral anoxia, and intraoperative neurophysiological monitoring.

Isolated Oculomotor Nerve Palsy as Presenting Symptom of Bilateral Chronic Subdural Hematomas: Two Consecutive Case Report and Review of the Literature

BACKGROUND

Isolated oculomotor nerve palsy (ONP) is caused most commonly by vascular disease, posterior circulation aneurysms, and inflammatory or traumatic injury. ONP usually occurs in chronic subdural hematoma (CSDH) as a common sign of cerebral herniation that typically is associated with a deterioration of consciousness.

CASE DESCRIPTION

We report 2 cases of bilateral CSDH who presented with ONP without deterioration of consciousness. An extensive literature review revealed this is an extremely rare finding. We also investigated all the possible pathogenic mechanisms producing nerve impairment and found a strong association with bilateral subdural hematoma. Vascular compression between posterior circulation arteries and tentorial edge abnormalities also could be involved. Vulnerability of the oculomotor nerve seems to be a necessary condition leading to clinical onset and is caused by predisposing factors to nerve damage, including vascular disease, head trauma, or herpes zoster infection.

CONCLUSIONS

Although isolated ONP is a very rare presentation of CSDH, a differential diagnosis is absolutely necessary, because surgical treatment allows good recovery of third nerve palsy in most of the cases.

Kernohan's notch and misdiagnosis of disorders of consciousness

A 69-year-old man presented with a sudden headache followed by unconsciousness. There was no head injury. The Glasgow Coma Scale (GCS) score was 3/15 and there was a left mydriasis, unreactive to light. The CT-scan showed a left acute subdural haematoma causing a remarkable mass effect. A supratentorial hemispheric craniotomy was performed. Nevertheless, after several weeks at the intensive care unit (ICU), the patient was still unresponsive to external stimuli and did not show any motor activity. A comfort care attitude was decided on with the family and the patient was extubated. However, a few days later, the patient subsequently showed a surprisingly favourable course, with improved wakefulness. Indeed, the GCS score improved, and the treatment plan was modified so that the patient benefited from rehabilitation. The MRI showed a right cerebral peduncle lesion, consistent with a Kernohan-Woltman notch phenomenon (KWNP). Six months later, the patient was able to walk and live quite normally.

[Kernohan-Woltman notch phenomenon secondary to a cranial epidural hematoma]

Kernohan-Woltman notch phenomenon is a paradoxical neurological manifestation which involves a motor deficit on the same side as the primary brain injury. It is produced mainly by acute or chronic subdural hematomas, and less frequently by post-traumatic epidural ones. It should be taken into consideration in cases of ipsilateral motor deficit, as it may lead to surgical procedures being performed on the incorrect side. We report the case of a 40 year old man who sustained a major head injury which was followed by a decreased level of consciousness and anisocoria. Computed tomography of the brain revealed a frontal and parietal epidural hematoma with right midline shift and uncal herniation. Craniotomy and drainage of the hematoma was performed, and on the sixth day after surgery it was observed that the patient had a brachio-crural right hemiparesis. Magnetic resonance imaging showed an ischemic area on the left capsule and cerebral peduncle consistent with the diagnosis of Kernohan-Woltman notch phenomenon.

Kernohan’s Notch: A Forgotten Cause of Hemiplegia—CT Scans Are Useful in This Diagnosis

Hemiparesis ipsilateral to a cerebral lesion can be a false localizing sign. This is due to midline shift of the midbrain resulting in compression of the contralateral pyramidal fibers on the tough dural reflection tentorium cerebelli. This may result in partial or complete damage to these fibers. Since these fibers are destined to cross in the medulla and innervate the opposite side of the body, this causes hemiparesis ipsilateral to the site of cerebral lesion. Computed tomography (CT) scans have not been used to support the diagnosis of this entity until now. We report a 68-year-old woman with a subdural hematoma who developed ipsilateral hemiparesis without any other explanation (Kernohan's notch). The CT of the head showed evidence of compression of the midbrain contralateral to the hematoma and was useful in the diagnosis. The purpose of this report is to increase the awareness of this presentation and to emphasize the utility of CT scans to support the diagnosis.

Neural tract injuries by brain herniations after head trauma

OBJECTIVES

: Little is known about the usefulness and findings of brain herniation on diffusion tensor tractography (DTT). Using DTT, we demonstrated neural tract injuries in 2 patients who showed subfalcine and trasntentorial herniations after subdural hematoma resulting from motor vehicle accident.

DESIGN

: Two patients and 6 age- and sex-matched, healthy volunteers were recruited for this study.

SETTING

: An inpatient rehabilitation unit.

MAIN OUTCOME MEASURES

: Diffusion tensor tractography for the patients was performed 5 weeks after onset.

RESULTS

: Diffusion tensor tractography of patient 1 showed complete injury of both cingulums at or around the rostrum of the corpus callosum, the fornix at the anterior and posterior body, and both corticospinal tracts at the pons. In addition, partial injury of both somatosensory tracts at the midbrain was also observed. Patient 2 showed complete injury of both cingulums above the body of the corpus callosum, the fornix at the anterior and posterior body, and right corticospinal tracts at the pons level and partial injury of the right somatosensory tract. We found that the fractional anisotropy values of all neural tracts, except fornix, in both patients and left somatosensory tract in patient 2 and voxel number for left somatosensory tract in patient 2 were decreased 2 SDs below that of normal controls.

CONCLUSIONS

: We determined that DTT would be a good technique for use in the detection of underlying lesions in patients with brain herniation.

Clinical usefulness of diffusion tensor imaging in patients with transtentorial herniation following traumatic brain injury

PRIMARY OBJECTIVE

This study investigated the clinical usefulness of diffusion tensor tractography (DTT) for elucidation of the corticospinal tract (CST) state in patients with transtentorial herniation (TH) following traumatic brain injury (TBI).

METHODS AND PROCEDURES

Eleven consecutive patients with TH were recruited among 175 patients with TBI. Patients who showed TH were classified into two groups according to DTT findings: Group 1: the integrity of CST was preserved, Group 2: the integrity of CST was disrupted at the cerebral peduncle (CP) or pons.

OUTCOMES AND RESULTS

Five patients belonged to Group 1 of TH, six patients to Group 2 of TH. On DTT of Group 1, fractional anisotropy values of the CP and pons along the CST in the affected hemisphere were lower than those of the unaffected hemisphere; however, the difference was not significant (p > 0.05). In Group 2, fractional anisotropy values of the CP and pons in the affected hemisphere were significantly lower than those of the unaffected hemisphere (p < 0.05).

CONCLUSIONS

It was found that DTT is useful in evaluation of the presence and the severity of CST injury in patients with TH following TBI.

Kernohan-Woltman notch phenomenon caused by an acute subdural hematoma

Uncal herniation through the tentorial notch is occasionally associated with false localizing ipsilateral hemiparesis, known as the Kernohan-Woltman notch phenomenon (KWNP). We report an 81-year-old female who presented with a decreased level of consciousness, a right mydriasis and an ipsilateral motor deficit caused by a large right hemispheric subdural hematoma that was immediately evacuated. The patient recovered well, although her right hemiplegia persisted. A follow-up MRI showed a residual lesion in the left cerebral peduncle, corresponding to KWNP. The presence of such a structural lesion suggests a poor prognosis for recovery from the initial motor deficit.