Neurocrit Care
https://doi.org/10.1007/s12028-018-0545-5

A DAY IN THE LIFE OF A NEUROCRITICAL CARE TRAINEE

Bilateral Bow Hunter’s Syndrome
Mimicking a Classic Seizure Semiology
Asher J. Albertson and Terrance T. Kummer*
© 2018 Springer Science+Business Media, LLC, part of Springer Nature and Neurocritical Care Society

Introduction
Bow Hunter’s Syndrome, or rotational vertebrobasilar
insufficiency, is a rare disorder characterized by posterior
circulation ischemia elicited by neck rotation. The term
was coined in 1978 when a 39-year-old man presented
with lateral medullary syndrome after practicing with a
bow in preparation for deer hunting [1]. His symptoms
were hypothesized to be caused by the rotation of his
neck while sighting an arrow resulting in dynamic, unilateral vertebral artery occlusion. Since then, the definition
of rotational vertebrobasilar insufficiency has been refined
to mechanical vertebral artery occlusion in the setting of
poor collateral flow, with most cases occurring transiently
[2]. The occlusion may have multiple etiologies including bone spurs, fibrous bands, chiropractic manipulation,
cervical disk herniation, and rarely trauma [2, 3]. Symptoms occur for a median duration of 12 months before
initial presentation and most commonly include vertigo,
visual changes, pain, nausea, vomiting, and syncope or
pre-syncope [2, 4]. Diagnosis may involve multiple imaging modalities including computed tomography (CT)
angiography, magnetic resonance angiography (MRA),
transcranial doppler, and digital subtraction angiography. Dynamic angiography in which the patient’s head is
rotated during imaging to demonstrate vertebral artery
occlusion is considered the gold standard [5].
Here, we report a challenging case of rotational vertebrobasilar insufficiency that presented to the neurological and neurosurgical intensive care unit (NNICU). This
case involved several diagnostic and management challenges—including an atypical history, a masquerading
set of symptoms, and bilateral lesions—that required
*Correspondence: kummert@wustl.edu
Department of Neurology Division of Neurocritical Care, Washington
University School of Medicine, 660 S. Euclid Avenue, Box 8111, St. Louis,
MO 63110, USA

complex decision-making and provided multiple learning
points for neurocritical care trainees.

Case Presentation
An 84-year-old woman with a history of rheumatoid
arthritis, major depressive disorder, and childhood seizures presented to our hospital with several days of vertigo and postural instability. At baseline, the patient was
wheelchair-dependent because of severe rheumatoid
arthritis. Two weeks prior to presentation, she suffered
an incidental fall out of bed and struck her head. She
was taken to a community emergency room where X-ray
imaging was unrevealing and she was discharged home.
After discharge, she suffered near-constant neck pain.
Three days prior to presentation, she began experiencing spells of postural instability, vertigo, and nausea.
These symptoms had not occurred prior to her fall out of
bed. She presented to our emergency room where a head
CT was unremarkable. A neck CT revealed a complex C1
vertebral fracture (Fig. 1a) as well as an odontoid fracture with posterior displacement (Fig. 1b) in the setting
of severe degenerative disease. She was placed in a cervical collar. On examination, she was mildly somnolent,
but arousable to voice and fully oriented. Her neurologic
examination was otherwise unremarkable. Notably, there
were no cranial nerve abnormalities, no areas of focal
weakness or sensory loss, and no ataxic signs.
Immediately after admission, she exhibited recurring,
stereotyped spells for which she was transferred to the
NNICU. These spells lasted approximately 30 s and were
characterized by sudden unresponsiveness to stimulation, sonorous breathing, and gaze deviation to either
the right or the left. Most strikingly, she exhibited classic fencer posturing with tonic extension of the right or
left arm and concurrent contralateral arm flexion. Spells
were followed by an immediate return to her mental status baseline.

Fig. 1 a Axial cervical spine CT demonstrating C1 fracture (arrowhead). b Sagittal cervical spine CT demonstrating dens fracture with posterior displacement (arrowhead). c EEG recording typical of activity during a spell demonstrating diffuse delta range slowing and lack of epileptiform activity

Given the patient’s history of childhood seizures, her
recent head trauma, and fencer posturing, we had a high
suspicion that these spells represented epileptic events.
We therefore monitored the patient on continuous video
electroencephalography (EEG) for several days while
anticonvulsant medications (levetiracetam, lacosamide,
and lorazepam) were trialed. These interventions did
not alter the frequency of observed spells, and none of
her events were associated with clear epileptiform activity. Instead, diffuse delta range slowing was the most
prominent electroencephalographic finding during spells
(Fig. 1c).
Coincident with her electrophysiological workup,
vascular studies were performed. A CT angiogram
(CTA) revealed a stenosis and likely dissection of the
left vertebral artery (Fig. 2a), and occlusion of the
right vertebral artery (Fig. 2b). Both the stenosis and
occlusion of the vertebral arteries were near the C1
fracture. At this point, staff began noticing that spells
seemed to be elicited with changes in position including bathing the patient or repositioning her in bed. An
MRI with MR angiography demonstrated no evidence
of stroke, but did demonstrate a patent right vertebral artery (previously occluded on CTA) as well as
diminutive bilateral posterior communicating arteries (Fig. 2c). The initial occlusion of the right vertebral
artery on CTA with subsequent resolution on MRA
suggested intermittent cervical occlusion and raised
the possibility of a dynamic vascular etiology for the
patient’s spells. She was briefly trialed on vasopressors

to a mean arterial pressure of 120 mmHg to optimize
collateral perfusion in the setting of dynamic flow
limitation. This also failed to mitigate her positiondependent spells.
Given the concern for a dynamic vascular etiology,
catheter vertebral artery angiography was performed.
Injection of the left vertebral artery initially demonstrated intact flow (Fig. 2d). Turning the patient’s head
15° left during the procedure elicited a typical spell and
demonstrated complete occlusion of the previously patent left vertebral artery (Fig. 2e; the right vertebral artery
was not injected). This, along with an intermittently patent right vertebral artery, suggested a diagnosis of bilateral rotational vertebrobasilar insufficiency resulting in
ischemic spells that mimicked a classic seizure semiology.

Management
Because of her frequent and debilitating spells, the risk
of brainstem stroke from dynamic vascular compression, and an unstable cervical spine, the patient underwent occipitocervical fusion. She was difficult to arouse
following surgery, raising concern for intraoperative
ischemia. A repeat brain MRI was performed which
unfortunately demonstrated extensive posterior circulation strokes (Fig. 2f ). She remained minimally arousable
on mechanical ventilation in the ICU for the next several days. Given the patient’s extensive brainstem injury
and resultantly poor prognosis, in consultation with her
family, care was redirected to prioritize comfort. She
was subsequently discharged to hospice.

Fig. 2 a CT angiogram curved planar reformation demonstrating stenosis of the left vertebral artery (arrowhead). b CT angiogram vascular reconstruction demonstrating occlusion of the right vertebral artery (arrowheads). c MR angiogram reconstruction demonstrating a subsequently patent
right vertebral artery (arrowheads). d Digital subtraction angiogram demonstrating intact flow within the left vertebral artery. e Digital subtraction
angiogram demonstrating lack of flow in the left vertebral artery (arrowhead) after turning the head 15° to the patient’s left. f Diffusion-weighted
MRI images demonstrating multifocal areas of posterior circulation infarct, including in the bilateral pons (inset)

Discussion
This patient’s case presented an unusual diagnostic challenge. The differential diagnosis of transient neurological syndromes generally includes, at a first pass, seizure,
ischemia, and migraine phenomena. Many other common conditions must also be considered including toxic

or metabolic abnormalities, alterations of intracranial
pressure, cardiac dysrhythmias, vasovagal syndromes,
orthostasis, and psychogenic syndromes. The stereotyped
nature of this patient’s spells, her sudden loss of responsiveness, and her gaze deviation were highly concerning
for seizure. Additionally, fencer positioning is classically

associated with frontal lobe seizures involving the supplementary sensorimotor area [6]. Her history of recent
head trauma and childhood seizures further elevated this
diagnosis on her differential. There were, however, also
several indicators of a vascular etiology: First, the association of spells with a change in position suggested a
dynamic, structural lesion. Second, the lack of a significant postictal period is inconsistent with most seizures.
Ultimately, the absence of electrographic seizures on EEG
during spells made a vascular etiology much more likely.
Though preceding studies (CT and MR angiography)
were concerning for a dynamic flow limitation, a conventional angiogram including head rotation was necessary
to definitively diagnose Bow Hunter’s Syndrome. When
considering this case, it is interesting to note that both
seizures [7, 8] and status epilepticus have been reported
as presenting symptoms of basilar occlusion [9].
In addition to its diagnostic teaching points, this case
is also novel and instructive in its etiology. Presentation
following trauma is unusual, and this patient’s symptoms
were both more acute and more severe than is typically
reported for Bow Hunter’s Syndrome [2]. This may be due
to the bilateral nature of this patient’s transient vertebral
artery occlusion and the minimal anterior-to-posterior
collateral flow due to diminutive posterior communicating arteries, resulting in profound brainstem ischemia.
The patient’s clinical course furthermore implicates
fencer posturing as an important sign of brainstem
ischemia. Fencer posturing, also known as the asymmetric tonic neck reflex, is a well described primitive reflex in
infants as well as adults with neurodegenerative diseases
[10]. Classic work in decerebrate cats demonstrated it to
be a vestibular reflex [11]. Fencer posturing is also frequently observed following mild traumatic brain injury
[12] and is hypothesized to be caused by transient neurovascular disruption of the vestibular nucleus in the
ventral pons. It is tempting to hypothesize that similar
transient disruptions repeatedly occurred in this patient
following obstruction of blood flow to the ventral pons
after positional vertebral artery occlusion. Abnormal
limb movements [13, 14] as well as convulsions [15] have
previously been reported following posterior circulation
ischemia.
This case, to our knowledge, is the first report of Bow
Hunter’s Syndrome presenting with fencer posturing
mimicking a seizure semiology. Diagnosis in neurology
is susceptible to cognitive errors in the use of heuristics
[16], and recognition of such errors is an important skill
for neurocritical care trainees to gain. This case specifically provides an opportunity to consider framing error,
anchoring error, and availability error (the relative frequency of seizures in the NNICU can make alternate
diagnoses appear less likely than clinical data suggest).

Although this patient’s diagnosis ultimately became
apparent through testing, the case unfortunately serves
to highlight the high risk of devastating stroke with
lesions impacting the posterior circulation.

Key Points
1. A unique case of bilateral rotational vertebrobasilar
insufficiency (Bow Hunter’s Syndrome) is presented.
2. The case had several elements which presented a significant diagnostic challenge:
• The acute and severe nature of the patient’s presentation after trauma
• 	 The likely involvement of bilateral vertebral arteries
• 	 Fencer posturing with loss of consciousness as a
rotation-induced symptom
3. While MR and CT angiography aided in the diagnosis and helped rule out alternative diagnoses,
dynamic catheter angiography was ultimately
required to make a definitive diagnosis.
Author’s Contributions
Both authors contributed equally to the design, writing, and publication
of this manuscript. Additionally, both authors directly cared for the patient
described within the manuscript.
Source of Support
Terrance T. Kummer has the following source of support: KO8 5K08NS09476003. Asher J. Albertson has the following source of support: American Heart
Association 17CPOST33660575.
Compliance with Ethical Standards
Conflict of interest
The authors declare that they have no conflict of interest.

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