Kernohan's phenomenon associated with left ruptured occipital arteriovenous malformation

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.

Ruptured Arteriovenous Malformation Presenting with Kernohan's Notch

AVMs are congenital lesions that predispose patients to intracranial hemorrhage and resultant neurological deficits. These deficits are often focal and due to the presence of local neurologic disruption from hemorrhage in the contralateral cerebral hemisphere. We present a rare case of a patient with ipsilateral neurological deficits due to Kernohan's Notch phenomenon resulting from hemorrhage from an AVM. A 31-year-old woman with seizures underwent MR and angiographic imaging which confirmed an unruptured left parietal AVM. The patient declined treatment and presented with obtundation 4 years later. Imaging revealed an acute left parietal ICH and SDH with significant mass effect. The patient underwent emergent hemicraniectomy and hematoma evacuation. Postoperatively, she made significant improvement and was following commands contralaterally with ipsilateral hemiplegia. MR imaging revealed right Kernohan's Notch. The patient had significant rehabilitation with neurological improvement. She eventually underwent elective embolization followed by subsequent surgical resection and bone replacement. Three years from the initial hemorrhage, the patient had only mild left-sided weakness and ambulates without assistance. A false localizing sign, Kernohan's Notch phenomenon, should be considered in the setting of AVM hemorrhage with paradoxical motor impairment and can be identified through MRI.

Venous anastomotic circle, multiple varices and oculomotor palsy--a rare coincidence

Oculomotor nerve palsy due to a venous varix arising from flow anomalies caused by a dural arteriovenous fistula (AVF) is a rare phenomenon. We report a case of surgical third nerve palsy with a rare underlying AVF as the cause and discuss in detail the patho-anatomy and its significance. A tentorial dural AVF mimicking the arterial circle was found with multiple varix formation causing compressive oculomotor palsy. This was treated successfully with Onyx™ injection with a satisfactory angiographic result and complete resolution of symptoms.

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.