Kernohan-Woltman notch phenomenon: an unusual cause of ipsilateral motor deficit

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.

Nonepileptic, Stereotypical, and Intermittent Symptoms After Subdural Hematoma Evacuation

Transient neurological deficits can occur in the setting of subdural hemorrhages with subsequent unremarkable electrodiagnostic and radiological evaluation. This scenario is rare and can be difficult for physicians to interpret. These transient neurological deficits are thought to result from relative ischemia, secondary to a lesser-known concept known as cortical spreading depolarization. These transient neurological deficits are thought to result from relative ischemia, secondary to a lesser-known concept known as cortical spreading depolarization, which may present clinically as nonepileptic, stereotypical, and intermittent symptoms (NESIS). In these instances, patients are often misdiagnosed as epileptics and committed to long-term antiseizure drugs. We present a 51-year-old patient developing acute global aphasia following the evacuation of a subdural hematoma, with no significant findings on laboratory, microbiological, electrodiagnostic, or radiological evaluation. The patient experienced spontaneous improvement and returned to baseline in the subsequent weeks. Increased awareness of NESIS as a cortical spreading depolarization phenomenon can improve patient care and prevent both unnecessary, extended medical evaluations and therapeutic trials.

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.

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)

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.

Diffusion tensor tractography in two cases of kernohan-woltman notch phenomenon

Kernohan-Woltman notch phenomenon (KWP) is an ipsilateral motor weakness due to compression of the contralateral cerebral peduncle. We report two cases of KWP following traumatic brain injury. In case 1, ipsilateral hemiplegia was noted after right subdural hemorrhage. Although magnetic resonance imaging showed no abnormal signal changes on cerebral peduncle, diffusion tensor tractography (DTT) revealed interruption of corticospinal tract (CST) at lower level of the midbrain level. In case 2, there was abnormal signal change of the right cerebral peduncle contralateral to the primary lesion and we could not reconstruct right CST. Case 1 showed unsatisfactory motor recovery even after 15 months, and follow-up DTT showed no change. In case 2, follow-up DTT was not performed, but her ipsilateral hemiparesis had almost disappeared during the 15 months. DTT would be useful in detecting ipsilateral hemiparesis due to KWP and the clinical course may differ according to the lesion characteristics.

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.

False localizing signs in traumatic brain injury

BACKGROUND

Hemiparesis ipsilateral to a mass-occupying lesion can be due to Kernohan-Woltman Notch Phenomenon (KWNP). This syndrome implies a false-localizing sign because clinical findings lead the examiner to an incorrect neuroanatomical diagnosis. The contralateral crus cerebri (pyramidal tract) is pressed against the tentorial incisum and a resultant hemiparesis is found on the same side of the lesion.

REVIEW

A detailed literature search of false-localizing signs is presented.

CONCLUSIONS

Not infrequently, patients presenting to a physiatrist may have incomplete records. The existence of false localizing signs may point the physician towards the wrong underlying pathology.

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

We report two cases of Kernohan's notch phenomenon secondary to chronic subdural hematoma detected by MRI. In the first case, the patient was drowsy with an oculomotor palsy and a hemiparesis ipsilateral to the chronic subdural hematoma. MRI in the post-operative period showed no abnormal signal or deformity of the crus cerebri. The neurological signs immediately resolved after trephination. In the second case, the patient was admitted with progressive decrease in their level of consciousness and ipsilateral hemiparesis with the chronic subdural hematoma. MRI on admission revealed an abnormal signal in the contralateral crus cerebri against the chronic subdural hematoma. After surgery, the mental state gradually recovered to normal with some degree of residual hemiparesis. In patients with chronic subdural hematoma, a compressive deformity of the crus cerebri, without abnormal signal on MRI, may predict a better neurological recovery in patients with Kernohan's notch phenomenon.

Transcranial Motor Evoked Potential Recording in a Case of Kernohan's Notch Syndrome: Case Report

OBJECTIVE AND IMPORTANCE

Compression of the cerebral peduncle against the tentorial incisura contralateral to a supratentorial mass lesion, the so-called Kernohan-Woltman notch phenomenon, can be an important cause of false localizing motor signs. Here, we demonstrate a case in which clinical, radiological, and electrophysiological findings were used together to define this syndrome.

CLINICAL PRESENTATION

A 21-year-old man sustained a left temporal depressed cranial fracture from a motor vehicle accident. Serial computed tomographic examinations demonstrated no evolution of hematomas or contusions, and he was managed nonsurgically with ventriculostomy for intracranial pressure control. Throughout his course in the neurosurgical intensive care unit, he displayed persistent left hemiparesis.

INTERVENTION

Further radiological and electrophysiological studies were undertaken in an attempt to explain his left hemiparesis. Brain magnetic resonance imaging demonstrated T2 prolongation in the central portion of the right cerebral peduncle extending to the right internal capsule. Electrophysiological studies using transcranial electrical motor evoked potentials revealed both a marked increase in voltage threshold, as well as a reduction in the complexity of the motor evoked potential waveform on the hemiparetic left side. This contrasted to significantly lower voltage threshold as well as a highly complex motor evoked potential waveform recorded on the relatively intact contralateral side.

CONCLUSION

This is the first time that clinical, radiological, and electrophysiological findings have been correlated in a case of Kernohan's notch syndrome. Compression of the contralateral cerebral peduncle against the tentorial incisura can lead to damage and ipsilateral hemiparesis. The anatomic extent of the lesion can be defined by magnetic resonance imaging and the physiological extent by electrophysiological techniques.

Lesión mesencefálica contralateral por hernia cerebral. Imagen en Resonancia Magnética de la Hendidura de Kernohan (Kernohan‘s Notch)

We report a case of a traumatic epidural hematoma with ipsilateral hemiparesis, due to the so-called Kernohan's notch. We document the injury with axial and coronal magnetic resonance imaging.

Magnetic resonance imaging findings of Kernohan-Woltman notch in acute subdural hematoma

OBJECTIVE AND IMPORTANCE

We report the case of a 73-year-old patient who presented a right motor deficit caused by an ipsilateral acute subdural hematoma. A magnetic resonance imaging (MRI) demonstration of Kernohan-Woltman notch phenomenon was obtained.

CLINICAL PRESENTATION

The woman sustained a major head injury at home, followed by loss of consciousness. On admission to the emergency room, she was comatose, anisochoric (left > right), and showed a reaction to pain with decerebrating movements of left limbs (Glasgow Coma Scale (GCS) 4/15). A right severe hemiparesis was observed. Cerebral computed tomography scan showed a large right hemispheric subdural hematoma. INTERVENTION AND POST-OPERATIVE COURSE: A wide right craniotomy was performed and the subdural hematoma evacuated. During the post-operative period, the level of consciousness gradually improved. A MRI performed about 2 weeks after operation showed a small area of abnormal signal intensity in the left cerebral peduncle. On discharge, the woman was able to communicate with others, but her right hemiparesis was still severe.

Sudden right-sided hemiparesis in a middle-aged woman

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