AUTHOR(S): Otsuki, Taisuke, M.D., Ph.D.;
Yoshimoto, Takashi, M.D., Ph.D.
Department of Neurosurgery, National Miyagi
Hospital and Division of Neurosurgery, Institute of
Brain Diseases, Tohoku University School of
Medicine, Sendai, Japan
Neurosurgery 35; 751-754, 1994
ABSTRACT: ENDOSCOPIC RESECTION OF a
cavernous angioma at the subthalamic region was
performed in a 33-year-old woman who presented
with diplopia and progressive hemiparesis caused by
recurrent hemorrhages. The entire surgical procedure
was done through an 8-mm guiding tube inserted
stereotactically from a frontal burr hole via an
approach that traversed the anterior limb of the
internal capsule. The patient's symptoms improved
after surgery. This is believed to be the first report
describing successful resection of a cavernous
angioma located at the subthalamic region.
KEY WORDS: Cavernous angioma; Diencephalon;
Endoscopy; Sterotactic surgery; Surgical technique
Cavernous angioma of the diencephalon is
uncommon. In a review of 164 cases of cerebral
cavernous angioma in 1976, Voigt and Yasargil (25)
described two cases of cavernous angioma in the
diencephalon, one in the hypothalamus with
Morgagni's syndrome, i.e., a syndrome of endocrine
dysfunction associated with hyperostosis of the
frontal bone, and one in the dorsal part of the
thalamus. In a more recent review by Simard, et al.
(21)
in 1986, the lesion occurred in the diencephalon in
two of 138 cases, namely, one in the thalamus (2) and
one in the hypothalamus (11), but none in the
subthalamus. Recently, surgical explorations of
thalamic and hypothalamic cavernous angiomas have
been reported (3,5,17,19,23). Surgical exploration of
cavernous angiomas at the subthalamic region,
however, has remained unmentioned.
CASE REPORT
This 33-year-old woman developed slight ptosis of
her right eyelid. She experienced headache, nausea,
and vomiting on the next day and noticed diplopia on
the following days. She was admitted to a nearby
hospital 7 days after the onset of symptoms.
Progressive left hemiparesis developed thereafter.
She was referred to our institution 3 weeks later.
Examination
On neurological examination, she exhibited
upward and downward gaze palsy with slight skew
deviation of the eyes and moderate left hemiparesis,
including her face, arm, and leg. Computed

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tomographic (CT) scans and magnetic resonance
(MR) images demonstrated a moderate enlargement
of the lateral ventricles with a right subthalamic
lesion of about 3.0 cm in maximal diameter extending
to the cerebral peduncle, suggesting a small
cavernous angioma associated with a hematoma
caused by recent hemorrhage (Fig. 1). Cerebral
angiography showed no vascular abnormalities such
as vascular stains and draining vessels.
Operation
One month after initial presentation the patient
underwent stereotactic endoscopic resection of the
subthalamic lesion. This was performed under
general anesthesia using a frontal burr hole to
approach the anterior limb of the internal capsule.
Most of the details of the devices and techniques
used for this surgical procedure have been reported
previously (13-15). Briefly, multiplannar MR imaging
(4-mm slices) was performed for planning the
trajectory of the guiding tube after a standard Leksell
stereotactic frame was fixed to the patient's head
under local anesthesia. The x, y, and z coordinates for
the center of the lesion, angle of the trajectory, and
depth of the lesion were calculated on MR images,
and the patient was transferred to the operating room
and anesthetized. After a burr hole had been made in
the right frontal bone, a small corticotomy was
performed, and a fine needle was inserted to confirm
the accuracy of the trajectory by aspirating the
liquified clot at the target site. Then, an 8-mmdiameter guide tube with an inner stylet was carefully
inserted to the target. The guiding device was fixed to
one of the needle holders of a standard Leksell
stereotactic frame with an adapter.
After removing the inner stylet, a rigid endoscope,
1.7 mm in diameter, having an outer sheath 2.2 mm in
diameter, was inserted to visualize the operating field.
The eye piece of the endoscope was attached to the
proximal needle holder of the Leksell apparatus
eccentrically, so that the tip of the endoscope could
be introduced along the wall of the guiding tube
(Fig. 2). The outer sheath was used to irrigate both
the tip of the endoscope and the operating field. The
lesion was partially encapsulated and adhered to a
structure near the wall of the third ventricle. It was
resected piecemeal using flexible tumor forceps.
Total resection of the angioma was achieved,
although a thin layer of fibrous capsule at the lateral
aspect of the wall of the third ventricle was not
removed but carefully coagulated by Nd; Yag laser. A
small piece of Gelfoam with dimensions of 5 × 5 × 10
mm was placed in the cavity after removal of the
angioma.
Postoperative course
The patient recovered from the anesthesia with
significant improvement in her gaze palsies and no
additional deficits. Her double vision and left
hemiparesis also resolved in the following days.
Histological diagnosis was cavernous angioma.
Postoperative CT and MR scans (Fig. 3) showed that
the angioma had been totally resected without
additional trauma to the brain, except for the fine line

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Neurosurgery 1992-98
October 1994, Volume 35, Number 4
751 Endoscopic Resection of a Subthalamic
Cavernous Angioma: Technical Case Report
Technical Case Report

DISCUSSION
Cavernous angiomas may cause hemorrhage,
seizures, and progressive neurological deficits (4,9,12,
16,24,25)
. Although the natural history of cavernous
angiomas is not fully understood, resection of
cavernous angiomas is recommended for
symptomatic patients if the lesions are accessible (6,7,
9,12,19,24,28)
. Surgical management of cavernous
angiomas, however, is not always simple, because
these lesions tend to be small and located deep in the
brain, so that location of the lesions by conventional
techniques may be difficult. Stereotactic radiographic
surgery, as an alternative to resective surgery, has so
far met with limited success in the case of cavernous
angiomas (8,27), and stereotactic needle biopsy of
cavernous angiomas for diagnostic evaluation
sometimes may cause massive and fatal hemorrhage.
The treatment of such malformations in the
diencephalon has been controversial (17). The recent
literature on brain stem cavernous angiomas,
however, suggests that surgical exploration should be
considered when the patient shows progressive and
repetitive neurological deficits caused by
hemorrhages (6,7,19,28). In our case, the malformation
was located in the subthalamic region, i.e., Forel's
field and the zona incerta (18). The patient's symptoms
of diplopia and hemiparesis progressed, and MR
imaging suggested recurrent hemorrhage. Because the
angioma was considered inaccessible by conventional
surgical techniques, we applied the endoscopic
approach to resect this small malformation (13). This
subthalamic cavernous angioma with a liquified clot
30 mm in the maximal diameter was removed
endoscopically through an 8-mm-diameter guide tube
using a frontal approach through the anterior limb of
the internal capsule between the caudate and the
globus pallidus.
The surgical approach adopted in our report is
unique but not totally new. In 1942, Meyers (10)
reported a transventricular approach to lesion the
ansa lenticularis for the treatment of parkinsonian
tremor and rigidity. This open procedure was
followed, in the 1950s and the 1960s, by stereotactic
approaches using various instruments and
thermocoagulation electrodes to injure the basal
structures, including the globus pallidus, ansa
lenticularis, Forel's field, and the ventrolateral part of
the thalamus (22,26).
Although the stereotactic endoscopic approach has
been considered an ideal method for resecting small
intracranial lesions with minimal invasiveness (1,20),
endoscopic excision of intraparenchymal lesions has
remained difficult. The authors have developed, in
this context, a new surgical approach using a

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stereotactic guide tube and fine endoscopes (13-15).
This approach allows the surgeons to use various
surgical instruments, including lasers, and makes
endoscopic resection of solid intraaxial lesions
possible. In the present case, an outer sheath of the
endoscope was used to irrigate both the tip of the
endoscope and the operating field to obtain better
visualization. Postoperatively, the patient's symptoms
improved dramatically without additional deficits.
We conclude that endoscopic resection should be
considered as an alternative in the treatment of
patients with small symptomatic cavernous angiomas,
especially if the angiomas are located at inaccessible
sites such as the deep diencephalons.
ACKNOWLEDGMENTS
We thank Dr. Masaharu Amagasa for referral of the
patient described in this report. We also appreciate
Dr. Toshikatsu Fujii's neuropsychological evaluation
of the patient.
Received, November 19, 1993.
Accepted, April 20, 1994.
Reprint requests: Taisuke Otsuki, M.D., Ph.D.,
Department of Neurosurgery, National Miyagi
Hospital, 100 Kassenhara, Takase, Yamamoto,
Watari, Miyagi 989-22, Japan.
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COMMENTS
This is a concise, well-written report about the use
of a stereotactic guide tube and fine rigid endoscope
to carry out resection of a cavernous malformation of
the diencephalon. Drs. Otsuki and Yoshimoto have
presented an excellent illustration of what can be
achieved by combining the precision of stereotaxy
with the optics of endoscopy to approach deep
lesions in eloquent brain.
Endoscopes have been used to access almost every
air- or fluid-filled cavity in the human body. Recent
interest in endoscopic neurosurgery has focused
primarily on disorders occurring within the clear fluidfilled cerebral ventricles. Otsuki and Yoshimoto have
shown that endoscopes also may offer an alternative
to the conventional management of lesions located
deep in the cerebral parenchyma. Essentially, they
have substituted a small rigid guide tube for brain
retractors and a small rigid endoscope for the
operating microscope, using miniaturized instruments
and a fiber-optic laser to perform the surgical
resection.
It can be difficult to establish a clear field of vision
when working endoscopically within the substance of
the brain. Visibility is somewhat improved when
exploring cysts or evacuated hematoma cavities. The
authors' method of irrigating through the endoscope's
outer sheath was reportedly effective in maintaining
visibility of the target. Another potentially limiting
factor is endoscopic hemostasis, which sometimes
can be difficult to achieve. The very factors that make
endoscopic neurosurgery a minimally invasive
procedure also make it difficult for the surgeon to
handle significant bleeding should this occur. I would
not recommend this approach for highly vascular
lesions.
The authors have presented a very nice example of
the use of stereotactic neuroendoscopy to remove a
deep lesion in eloquent brain with minimal
invasiveness. They have reported this technique of
"open-system endoscopy" previously for removal of
cavernous malformations and malignant parenchymal
tumors (1). Other neurosurgical applications include
"closed-system endoscopy" to perform therapeutic
procedures within the cerebral ventricles through burr

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9.

hole exposures and "endoscope-assisted craniotomy"
to look around corners and limit the need for
excessively large bony exposures at the cranial base.
Alan R. Cohen
Cleveland, Ohio
REFERENCES: (1)
Otsuki T, Jokura H, Yoshimoto T: Stereotactic
guiding tube for open-system endoscopy: A
new approach for the stereotactic endoscopic
resection of intra-axial brain tumors.
Neurosurgery 27:326-330, 1990.

The paper of Otsuki and Yoshimoto presents the
very skillful management of a patient with a deepseated thalamic cavernoma with subthalamic
hemorrhage. The indication for active treatment was
given because of the symptomatic lesion. The authors
show how important the combination of stereotactic
guidance of the endoscope is. The special technique
of Otsuki and Yoshimoto is to use an open 8-mm
working tube, in which the thin 1.7-mm lens scope is
placed, and the remaining diameter is free for the
working instruments. With this equipment, it is
possible to remove larger pieces of tissue and to have
a larger action radius for the instruments under optic
control. The technique described offers another
example of how to combine microsurgical
manipulation with endoscopic visual control for the
surgery of deep-seated lesions, using the same
philosophy as in surgery of deep-seated aneurysms to
avoid retraction of important structures.
Axel Perneczky
Mainz, Germany

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1.

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Figure 1. Preoperative CT scan and magnetic
resonance (MR) T1-weighted images. Left, CT scan
demonstrating a mixed-density lesion at the right
subthalamic region and dilatation of the lateral
ventricles. Middle, MR sagittal image showing a
heterogeneous signal intensity lesion located at the
subthalamic region extending to the cerebral
peduncle. Right, MR oblique image, 45 degrees from
the AC-PC line, obtained for surgical planning,
demonstrating that the lesion is accessible from the
frontal cortex through the anterior limb of the internal
capsule.

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Figure 2. Diagram illustrating the equipment for
open-system endoscopic surgery. a, Guide tube, 8
mm in diameter, fixed to one of the needle holders of
a standard Leksell stereotactic frame at the proximal
end (*). b, Rigid endoscope, 1.7 mm in diameter,
having an outer irrigation sheath, 2.2 mm in diameter,
attached to the proximal needle holder of the Leksell
apparatus (**). c, Window to insert such
microsurgical instruments as aspirators, flexible
forceps, and laser fibers to resect an intraaxial lesion.

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Figure 3. Postoperative CT scan and T1-weighted
MR images. Left, CT scan performed 14 days after
surgery showing total resection of the angioma and
improvement in the ventricular dilatation. Middle,
MR sagittal image obtained during the fourth
postoperative week showing total resection of the
angioma and the normalization of the configuration
of the midbrain and the diencephalon. Right, MR
oblique image, 45 degrees from the AC-PC line,
obtained during the fourth postoperative week,
demonstrating the fine line of the trajectory used to
resect the angioma from the frontal burr hole through
the anterior limb of the internal capsule.

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