Kernohan-Woltman Notch Phenomenon in Neuroimaging
Summary
The Kernohan-Woltman notch phenomenon is a paradoxical neurological event in which a supratentorial mass lesion induces a midline shift and causes compression of the contralateral cerebral peduncle against the tentorial edge. This compression produces motor deficits on the same side as the primary lesion, defying the usual contralateral presentation associated with corticospinal tract injury. Historically identified through clinical observation and post-mortem studies, the phenomenon has been confirmed and characterised in vivo by modern imaging techniques. High-resolution magnetic resonance imaging (MRI) can directly visualise peduncular indentation, while functional modalities such as positron emission tomography (PET) have revealed metabolic alterations in the affected peduncle. Recognition of this false localising sign is critical to accurate diagnosis, surgical planning and avoidance of wrong-side interventions. Ongoing research is refining the anatomical risk factors, such as tentorial notch variations, and exploring prognostic imaging markers that correlate with motor recovery after decompressive surgery.
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Kernohan-Woltman Notch Phenomenon in Neuroimaging publication trend
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Technical terms
Kernohan-Woltman notch phenomenon: Paradoxical ipsilateral motor deficit caused by compression of the contralateral cerebral peduncle against the tentorial edge owing to a supratentorial mass lesion.
False localising sign: Clinical finding in which neurological deficits appear on the same side as, rather than opposite to, a brain lesion, misleading localisation efforts.
Uncal herniation: Displacement of the medial temporal lobe (uncus) through the tentorial notch, compressing midbrain structures.
Cerebral peduncle: Bundled white-matter tracts in the midbrain conveying motor fibres from the cortex to the brainstem and spinal cord.
Corticospinal tract: Descending fibre pathway originating in the motor cortex that controls voluntary movement of the body.
References
- Kernohan–Woltman notch phenomenon in patient with subdural hematoma and ipsilateral hemiparesis in Bukavu. Clinical Case Reports (2023).
- A case of Kernohan-Woltman notch phenomenon caused by an epidural hematoma: the diagnostic and prognostic value of PET/CT imaging. BMC Neurology (2022).
- Variations of Tentorial Notch Anatomy in Autopsy and NCCT of Head Injury Patients to Correlate Its Impact over Brainstem—An Observational Study. Indian Journal of Neurotrauma (2024).
- Kernohan Woltman notch phenomenon caused by subdural chronic hematoma: Systematic review and an illustrative case. Annals of Medicine and Surgery (2022).
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