Brain & Development 29 (2007) 189–192
www.elsevier.com/locate/braindev

Case report

Lower brainstem dysfunction in an infant with persistent
primitive trigeminal artery
Tohru Okanishi a,*, Yoshiaki Saito a, Shiho Miki b, Jun-ichi Nagaishi b, Keiichi Hanaki c,
Yutaka Tomita d, Chisako Fukuda d, Shinya Fujii e, Kazunori Fujiwara f,
Katsuyuki Kawamoto f, Fumiko Hata f, Yoshihiro Maegaki a, Kousaku Ohno a
a

Division of Child Neurology, Institute of Neurological Sciences, Faculty of Medicine, Tottori University, Japan
b
Division of Pediatrics and Perinatology, Faculty of Medicine, Tottori University, Japan
c
Department of Women’s and Children’s Family Nursing, Faculty of Medicine, Tottori University, Japan
d
Department of Pathological Science and Technology, School of Health Science, Faculty of Medicine, Tottori University, Japan
e
Division of Radiology, Faculty of Medicine, Tottori University, Japan
f
Division of Otolaryngology, Head and Neck Surgery, Faculty of Medicine, Tottori University, Japan
Received 7 July 2006; received in revised form 15 August 2006; accepted 16 August 2006

Abstract
A 6-month-old boy with persistent primitive trigeminal artery (PPTA) presented with stridor, dysphagia, delayed motor development and postural neck and shoulder dystonia. Magnetic resonance imaging / angiography and ultrasonography revealed PPTA,
with ﬂow from the dilated basilar artery to the right internal carotid artery, lower brainstem compression by the dilated basilar
artery, and cerebellar vermis hypoplasia. Evoked potentials showed lower pons and medulla oblongata functional disruption. These
lesions may be related to vascular etiology in the lower brainstem or to congenital malformation syndrome involving infratentorial
structures. The relationship of this condition to Möbius syndrome is discussed.
Ó 2006 Elsevier B.V. All rights reserved.
Keywords: Primitive trigeminal artery; Dysphagia; Medulla oblongata; Cerebellar vermis hypoplasia; Möbius syndrome

1. Introduction
Primitive trigeminal artery (PTA) appears in the
developing brain at the 3–5 mm embryo stage, and is
one of the embryonic arteries that connect the dorsal
aorta (future internal carotid arteries) and the longitudinal neural arteries (future basilar artery) [1]. Persistent
PTA (PPTA) is the most common anomaly of the carotid-basilar anastomosis, and is observed in 0.1–0.6% of
angiograms [2]. Although most individuals with PPTA
remain asymptomatic, some manifest with clinical
*

Corresponding author. Tel.: +81 859 38 6777; fax: +81 859 38
6779.
E-mail address: oknsoknsokns@yahoo.co.jp (T. Okanishi).
0387-7604/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.braindev.2006.08.008

symptoms related to cranial nerve root compression by
the PPTA [2], or to brainstem ischemia, infarction and
intracranial hemorrhage that result from accompanying
vascular anomalies and aneurysms [3–5]. A rare case of
PPTA that was complicated with lower brainstem dysfunction and lower vermian hypoplasia is described.

2. Case report
A Japanese boy (birth weight, 2924 g; head circumference, 33 cm) with no birth asphyxia was delivered at
40 weeks gestation by cesarean section, resulting from
premature membrane rupture. In the neonatal period,
feeding diﬃculty and poor weight gain were noted.

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Upon hospital admission at four months of age,
weight, height and head circumference were 4620 g
( 3.1 SD), 57.7 cm ( 2.6 SD), and 40.0 cm ( 1.2 SD),
respectively. The auricular upper portion was thin, and
funnel chest was present; with retraction augmented in
a see-saw respiration pattern. Inspiratory and expiratory
stridor was noted, which was aggravated during crying
and associated with a gurgle sound in the pharynx. Deep

tendon reﬂex and muscle tonus at rest were normal,
although in the prone position there was prominent
retraction of both shoulders and dorsiﬂexion of the
neck. Fisted ﬁngers with adducted thumbs limited grasping and toy holding to only a few seconds. Muscle tonus
and motion of lower extremities were normal; as was
facial expression, for age. Tracking of moving objects
with both eyes and showing interest in surroundings

Fig. 1. T1-weighted brain magnetic resonance imaging (A,B). Compression on the lower brainstem by a dilated basilar artery is noted, and the lower
half of the cerebellar vermis is absent (A). Medulla oblongata is compressed by the basilar artery, although there is no evidence of vagal nerve root
compression (B).

Fig. 2. Magnetic resonance angiography (A–C) and color doppler US (D) of cranial and cervical vessels. The PPTA (A,B,D, arrows) connects the
basilar artery and the right internal carotid artery. No aneurysm or arteriovenous malformation was present in the craniocervical vascular system.

T. Okanishi et al. / Brain & Development 29 (2007) 189–192

was also apparently normal. However, vestibulo-ocular
reﬂex was attenuated and response to auditory stimuli
mild to weak. Sternocleidomastoid muscle was not
atrophic, and hypertonic due to the cervical dystonia.
Blood gas, lactate, thyroid function, screening tests
for metabolic disorders and G-banded chromosomal
analysis were normal. Magnetic resonance imaging /
angiography revealed a dilated basilar artery (Fig. 1)
and the presence of a right PPTA (Figs. 2A and B). Ventral pons and medulla oblongata were compressed and
deformed by the dilated basilar artery (Fig. 1A). Both
anterior cerebral arteries appeared to originate from
the communicating artery in the right internal carotid
artery extension (Fig. 2B). Left vertebral artery was
dilated (Fig. 2C), although no other abnormalities were
observed in the cerebrovascular system.
Lower cerebellar vermis was hypoplastic (Fig. 1B).
Cerebral cortex, white matter myelination, basal ganglia
and cerebellar hemisphere were normal. Doppler ultrasonography (US) showed a blood ﬂow through the
PPTA, from the basilar artery to the right internal carotid artery (Fig. 2D). Electroencephalography was normal
for age. Brainstem auditory evoked potentials were
attenuated, showing only a trace of wave I and V. Otoacoustic emissions were negative. Median nerve short-latency somatosensory evoked potentials showed a
delayed N18 latency with right side stimulation, and
an absence of N20 and N30 with left side stimulation.
R1 latency was markedly delayed (17.4–18.8 ms; normal
10.1 ± 0.5 ms), and R2 and R2’ components were absent
on blink reﬂex. Motor nerve conduction velocity was
normal. Chest computed tomography revealed atelectasis in the dorsal lung bilaterally, suggesting the presence
of aspiration. Cardiac US showed normal results, and
abdominal US showed mildly small right kidney with
a 40 mm diameter in the long axis.
After admission, weight gain of 35 g/d was achieved
by nasogastric tube feeding. Upper gastrointestinal series showed a normal coordination pattern of oropharyngeal muscles, although the initiation of swallowing reﬂex
appeared diminished. Patient head control improved
gradually, but remains incomplete at 6 months of age.
He can now eat orally small part of his meal, and the laryngeal stridor has been ameliorated.

3. Discussion
In the present case, PPTA alone cannot account for
the clinical symptoms. Basilar artery compression on
the ventral brainstem, to a degree that is often encountered in the elderly, can explain the brainstem dysfunction, including the primary involvement of the
auditory pathway. Accompanying developmental
defects in the central nervous system may be assumed
to fully explain the clinical picture of this patient.

191

Möbius syndrome is characterized by congenital
paralysis of the 6th and 7th nerves. Since these motor
nuclei are located in the lateral tegmentum of the
brainstem, which corresponds to the watershed area,
vascular etiology may explain the pathophysiology
of this syndrome [6,7]. Such an ischemic lesion during
the embryonic period, usually not visible with neuroimaging, can involve the 8th to 10th cranial nerve
nuclei, which results in feeding and respiratory symptoms, and auditory disturbance [7,8], similar to that
of the present patient. Premature regression of carotid-basilar blood supply, or a delayed basilar artery
formation, may be causative in some cases of Möbius
syndrome [6]. Thus, it is interesting that Klippel–Feil
syndrome, another disease of vertebral-basilar artery
disruption, is associated with facial nerve paresis,
inner ear developmental defects, and rarely, with
PPTA [9]. Ischemic insults during the fetal period,
possibly through premature absorption of otic or stapedial arteries, may be related to the otolaryngological abnormalities of Klippel-Feil syndrome [7], in a
similar manner to those of the present patient. Thus,
the present patient may be an atypical Möbius syndrome subject.
PPTA also accompanies non-vascular malformations, including Chiari malformation type 1, cerebellar
cyst, and polycystic kidney [10,11]. Although these
might be accidental associations, in the present patient,
the dystonia and cerebellar vermis hypoplasia may represent a congenital malformation, where the vascular
anomalies and resultant brainstem ischemic lesions are
part of its manifestations. The etiology of PPTA in the
present patient may contribute to broaden the spectrum
of vertebral-basilar artery disruption to a category of
malformation syndromes involving the primordial cranial vascular system and other central nervous system
structures.

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