Clinical Neurology and Neurosurgery 101 (1999) 122 – 124

Case report

Magnetic resonance imaging findings of Kernohan–Woltman
notch in acute subdural hematoma
Luciano Mastronardi a,*, Fabrizio Puzzilli a, Andrea Ruggeri a, Antonio Guiducci b
a
b

Sandro Pertini Hospital, Di6ision of Neurosurgery, Roma, Italy
Institute of Pathological Anatomy, Ci6ilian Hospital, Terni, Italy

Received 14 August 1998; received in revised form 25 January 1999; accepted 25 January 1999

Abstract
Objecti6e 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. Inter6ention and post-operati6e 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. © 1999 Elsevier Science B.V. All rights reserved.
Keywords: Acute subdural hematoma; Ipsilateral hemiparesis; Kernohan – Woltman notch; Magnetic resonance imaging; Major head injury

1. Introduction

2. Case report

The compression of a contralateral cerebral peduncle
against the edge of the tentorium caused by a supratentorial mass, with ipsilateral motor deficit, was first
described by Kernohan and Woltman [1], who observed
this phenomenon in a patient suffering from a right
fronto-temporal brain tumor. Subsequently, several observations have been reported in patients with major
head injury and brain tumors [2 – 8]. We describe a case
of Kernohan–Woltman notch phenomenon (KWNP)
secondary to acute post-traumatic subdural hematoma,
in which the damage of contralateral cerebral peduncle
has been verified by post-operative cerebral magnetic
resonance imaging (MRI).

On going down the staircase in her home, a 73-yearold woman slipped along steps and sustained a severe
head injury, immediately followed by loss of consciousness. On first neurological examination in the emergency room, she appeared to be comatose, with a
Glasgow Coma Scale (GCS) of 4/15. Pupils were anisochoric (left\right) and a decerebrating reaction with
left limbs was observed. A severe motor deficit on right
hemisoma was also present. Cerebral computed tomography (CT) scan urgently performed showed a large
right hemispheric subdural hematoma and shift to the
left of midline structures and ventricles (Fig. 1). A wide
right craniotomy was performed and an about 2 cm
thick subdural hematoma was evacuated. Intracranial
pressure monitoring was obtained with a subdural
device and the increase of values observed during the
first days after operation were easily controlled with
hyperventilation and osmotics. The level of conscious-

* Corresponding author. Present address: Via Archimede 120,
00197 Roma, Italy. Tel.: +39-6-855-1729; fax: +39-6-321-6925.
E-mail address: mastro@tin.it (L. Mastronardi)

0303-8467/99/$ - see front matter © 1999 Elsevier Science B.V. All rights reserved.
PII: S 0 3 0 3 - 8 4 6 7 ( 9 9 ) 0 0 0 1 7 - 7

L. Mastronardi et al. / Clinical Neurology and Neurosurgery 101 (1999) 122–124

123

ness gradually improved and anisochoria disappeared a
few days after surgery, whereas the severity of right
motor deficit remained unchanged. A MRI performed
about 2 weeks after the operation (Fig. 2) showed a
small roundish area in the left cerebral peduncle, hypointense on T1-weighted images and hyperintense on
T2. On discharge, the woman was able to communicate
with others with easy sentences and to understand
commands, but her right motor deficit was still very
severe.

3. Discussion
KWNP can be the cause of false localizing motor
sign. The large right acute subdural hematoma observed in our patient produced an ipsilateral transtentorial uncal herniation and a compression of contralateral
cerebral peduncle against the edge of the tentorium,
with severe damage of the left corticospinal tract and a
transient lesion of the Edinger – Westphal nucleus of the
left third cranial nerve. The MRI performed 2 weeks
after the operation confirmed this interpretation, revealing a small roundish area, hypointense on T1- and
hyperintense on T2-weighted images, in correspondence
of the left cerebral peduncle (Fig. 2). The poor quality
of the urgent cerebral CT scan and the superiority of
MRI in the detection of traumatic lesions [3,9,10],
especially those of brain stem, may explain the lack of
demonstration of this lesion on first CT scan.
Cohen and Wilson [2] first described the MRI findings of KWNP in a young patient with left acute
post-traumatic extradural hematoma. The cerebral
Fig. 2. Post-operative cerebral MRI. Small roundish area, (a) hypointense on T1- and (b) hyperintense on T2-weighted images, in
correspondence of the left cerebral peduncle.

Fig. 1. CT scan urgently performed. Large right subdural hematoma
and left shift of midline structures and ventricles.

MRI performed 1 week after operation showed a small
roundish area of hyperintensity in the right cerebral
peduncle in T2-weighted images. These findings are
overlapping with those of our case and of other reports
[4,6–8]. In the case described by Itoyama et al. [3], in
which the KWNP was observed in a patient with
chronic subdural hematoma, the pre-operative MRI
showed a deformity of crus cerebri; the MRI performed
9 days after surgery revealed a marked reduction of
deformity of the cerebral peduncle, with improvement
of hemiparesis. Reich et al. [11] analyzed MRI images
in the sagittal planes and correlated them with clinical
changes in patients with transtentorial and foramen
magnum brain herniation. In acute illnesses, MRI abnormalities anticipated or confirmed clinical signs of
brain herniation, whereas in chronic cases, clinical and

124

L. Mastronardi et al. / Clinical Neurology and Neurosurgery 101 (1999) 122–124

MRI correlated less well: MRI evidence of herniation
anticipated the clinical manifestations or identified patients with reversible clinical deficits (which would correlate with improvement of clinical findings) [11].
Therefore, the mass effect quickly produced by acute
extradural or subdural hematomas can seldom produce
severe and irreversible ischemic damage of contralateral
cerebral peduncle, presumably caused by stretching and
occlusion of small perforating arteries or by their compression at the site of the tentorial notch.
In accordance with Zafonte and Lee [8], little is
known about the functional outcome of patients with
post-traumatic KWNP. MRI confirmation of the clinical suspect adds useful prognostic information. Therefore, even if MRI cannot be considered a routine
examination in major head trauma patients, it should
be always performed in cases in which neurological
signs are not clearly explained with the usual physiopathological mechanisms and cerebral CT scan.

References
[1] Kernohan JW, Woltman HW. Incisura of the crus due to
contralateral brain tumor. Arch Neurol 1928;274–87.

.

[2] Cohen AR, Wilson J. Magnetic resonance imaging of Kernohan’s notch. Neurosurgery 1990;27:205 – 7.
[3] Itoyama Y, Fujioka S, Ushio Y. Kernohan’s notch in chronic
subdural hematoma: findings on magnetic resonance imaging. J
Neurosurg 1995;82:645 – 6.
[4] Jones KM, Seeger JF, Yoshino MT. Ipsilateral motor deficit
resulting from a subdural hematoma and a Kernohan notch. Am
J Neuroradiol 1991;12:1238 – 9.
[5] Kanis KB, Ropper AH, Adelman LS. Homolateral hemiparesis
as an early sign of cerebellar mass effect. Neurology
1994;44:2194 – 7.
[6] Namura S, Kang Y, Matsuda I, Kamijyo Y. Magnetic resonance
imaging of sequelae of temporal lobe herniation secondary to
traumatic acute subdural hematoma: Kernohan’s notch and
posterior cerebral artery territory infarctions contralateral to the
supratentorial lesion — case report. Neurol Med Chir (Tokyo)
1997;37:32 – 5.
[7] Yamasaki F, Kodama Y, Hotta T, Yuki K, Taniguchi E,
Hashizume A. Magnetic resonance imaging of Kernohan’s notch
in chronic subdural hematoma. No To Shinkei 1997;49:563–6.
[8] Zafonte RD, Lee CY. Kernohan – Woltman notch phenomenon:
an unusual cause of ipsilateral motor deficit. Arch Phys Med
Rehabil 1997;78:543 – 5.
[9] Gentry LR, Godersky JC, Thompson BH. MR imaging of head
trauma: review of the distribution and radiopathologic features
of traumatic lesions. Am J Neuroradiol 1988;9:101 – 10.
[10] Gentry LR, Godersky JC, Thompson BH. Traumatic brain stem
imaging: MR imaging. Radiology 1989;171:177 – 87.
[11] Reich JB, Sierra J, Camp W, Zanzonico P, Deck MD, Plum F.
Magnetic resonance imaging measurements and clinical changes
accompanying transtentorial and foramen magnum brain herniation. Ann Neurol 1993;34:748 – 9.