CASE REPORT

Sinking Skin Flap Syndrome
A Case of Improved Cerebral Blood Flow After Cranioplasty
Tsukasa Isago, MD,* Motohiro Nozaki, MD,* Yuji Kikuchi, MD,* Takashi Honda, MD,* and
Hiroaki Nakazawa, MD†

Abstract: Sinking skin flap syndrome is defined as a series of
neurologic symptoms with the skin depression at the site of cranial
defect, which develop several weeks to months after large external
cerebral decompression.
The case of a 28-year-old female with the sinking skin flap
syndrome is reported together with the evaluation of cerebral blood
flow using xenon computed tomography (CT). Although her general
condition stabilized within 7 months after the injury, the skin of the
bilateral temporal regions was markedly depressed due to large bone
defects. She was confined to bed and showed reduced levels of
consciousness. We decided to treat this case by performing cranioplasty with a hydroxyapatite ceramic implant. Not only were good
cranial contour reconstructed after cranioplasty, but neurologic conditions were also improved after cranioplasty.
Regarding the change in cerebral blood flow in the present case,
as measured with xenon CT, the cerebral blood flow 3 days after the
injury was 18.7 ⫾ 12.3 mL/100 mL/min and 26.5 ⫾ 11.6 mL/100
mL/min in the left and right hemispheres, respectively. After the
bilateral cranioplasty, it had increased by approximately 2-fold to
36.4 ⫾ 23.2 mL/100 mL/min in the left hemisphere and approximately 1.5-fold to 43.8 ⫾ 23.3 mL/100 mL/min in the right hemisphere as compared with the levels obtained 3 days after the injury.
Therefore, xenon CT appears to be useful in the monitoring of
regional cerebral blood flow in patients with cranial bone defects
that are directly affected by atmospheric pressure and in predicting
functional prognosis. For the sinking skin flap syndrome cases,
cranioplasty is not only useful for cerebral protection and improvement of appearance, but cranioplasty is also useful for improving
neurologic symptoms.
(Ann Plast Surg 2004;53: 288 –292)
Received October 9, 2003 and accepted for publication, after revision,
December 31, 2003.
From the *Department of Plastic and Reconstructive Surgery, Tokyo Women’s Medical University, Tokyo, Japan; and the †Department of Plastic
and Reconstructive Surgery, National Disaster Medical Center, Tokyo,
Japan.
Reprints: Tsukasa Isago, MD, Department of Plastic and Reconstructive
Surgery, Tokyo Women’s Medical University, 8 –1 Kawada-cho, Shinjuku-ku, Tokyo, Japan 162– 8666. E-mail: isago@prs.twmu.ac.jp
Copyright © 2004 by Lippincott Williams & Wilkins
ISSN: 0148-7043/04/5303-0288
DOI: 10.1097/01.sap.0000106433.89983.72

288

S

inking skin flap syndrome (SSFS) is defined as serious
disabling neurologic deficits and impairment of the general status with concave deformity and relaxation of the skin
flap, which develop several weeks to months after large
craniectomy1,2. In general, large cerebral decompression is
performed to reduce high intracranial pressure. The cranial
defect produced by large craniectomy is directly affected by
atmospheric pressure. As cerebral swelling improves, the skin
at the cranial defect gradually sinks due to atmospheric
pressure to deform cerebral tissue. The neurologic symptoms
of SSFS include headache, vertigo, tinnitus, fatigue, loss of
concentration, loss of memory, depression, dysphagia,
apraxia, paresis of extremities, and convulsions. This paper
reports the case of large cranial bone defect, which was
treated with large hydroxyapatite ceramic implant. Also included are the improved neurologic symptoms of SSFS by
cranioplasty and the evaluation of cerebral blood flow using
xenon computed tomography (CT).

CASE REPORT
A 28-year-old female was hospitalized at an emergency
care center with bruising over her whole body and consciousness disorder because she jumped out of a fourth floor
window. On admission, she had a consciousness level of
coma and unequal pupils (right ⬎ left). She also had severe
head injuries, depressed skull fracture, pelvic, and vertebral
fractures, and open fracture of the toes of her right foot. Since
a head CT revealed intracerebral and subarachnoid hemorrhage, an emergency bilateral cranial decompression to remove hematoma was performed by a neurosurgeon. The right
surgical site was then incised for drainage and debridement
due to infection. Although her general condition stabilized
within 7 months, the skin of the bilateral temporal regions
was markedly depressed due to large bone defects (Fig. 1).
She was bedridden with neurologic symptoms, such as loss of
concentration, loss of memory, depression, dysphagia, and
paresis of extremities. Although her eyes were open, she did
not speak at all. She was under nutritional control with tube
feeding. Simultaneous bilateral cranioplasty was considered;
however, it was considered that the procedure might result in

Annals of Plastic Surgery • Volume 53, Number 3, September 2004

Annals of Plastic Surgery • Volume 53, Number 3, September 2004

FIGURE 1. Seven months after the removal of hematoma by
bilateral cranial decompression.

a shortage of cranial skin because the size of the left and right
bone defects was as large as 13 x 8 cm and 8 x 5 cm,
respectively. It was thus decided that cranioplasty be per-

Sinking Skin Flap Syndrome

formed in 2 stages and initiated from the left side because of
the larger size of the bone defect on that side. A bone defect
model was prepared from head CT images and modified so
that it would include the thickness of the temporal muscle. A
hydroxyapatite ceramic implant was prepared using this
model, which was used for the cranioplasty for the left bone
defect (Fig. 2A and B). The surgery was cooperatively
performed under general anesthesia by a plastic surgeon and
a neurosurgeon. To avoid suturing the skin flap just over the
implant, the incision was made slightly outside the scar from
the previous craniectomy, the skin and the dura were detached carefully, and the area of cranial bone defect was
completely exposed and complete hemostatic control was
gained. The prepared hydroxyapatite ceramic implant was
then inserted. Since the hydroxyapatite ceramic implant fit
the bone defect, modification of the shape of the implant was
unnecessary. At that time, the dura was raised and fixed in
place by using a hole created in the center of the hydroxyapatite ceramic implant, with the implant itself fixed to the
surrounding bone with silk thread twine. Extradural and
subcutaneous drains were then inserted, and the skin was
sutured to complete the procedure, which took approximately
3 hours and during which the volume of blood loss was only
200 mL. Depression improved around 2 weeks postoperatively. The training of oral intake of food relieved dysphagia
and incorrect deglutition, allowed her to feed herself using a
spoon, and eliminated the need for tube feeding. She also
became able to perform smoothly coordinated actions of the
upper extremities, such as changing her pajamas and doing up
buttons. Although she could not walk because of paralysis of
the lower extremities due to pelvic fracture and lumber
vertebra pressure fracture, she became able to move using a
wheelchair. Thus, general improvement of her neurologic

FIGURE 2. A, Cranial bone defect on the left temporal region. B, Hydroxyapatite ceramic implant fit the cranial bone defect.
© 2004 Lippincott Williams & Wilkins

289

Isago et al

Annals of Plastic Surgery • Volume 53, Number 3, September 2004

symptoms was observed postoperatively. However, she remained expressionless and speechless, despite becoming able
to understand easy words. A hydroxyapatite ceramic implant
for the right cranial defect was prepared in the same manner
as for the left cranial defect. The cranioplasty of the right
cranial defect was performed 4 months after the first cranioplasty. After the cranioplasty for the right cranial defect was
completed, she gradually began smiling and started to laugh
aloud. Neurologic symptoms observed preoperatively, such
as loss of concentration, loss of memory, depression, dysphagia, and paresis of extremities, started to improve around 2
weeks postoperatively. Dysphagia and incorrect deglutition
disappeared within 2 months postoperatively, and the patient
was able to feed herself using a spoon and was able to
perform coordinated actions using the upper extremities, such
as changing her pajamas and doing up buttons. Further, she
was able to speak an increasing number of words, said her
name, repeated words given to her, and sang songs, although
she could not speak a word 1 month after the right cranioplasty (Fig. 3).

FIGURE 3. Eight months after left cranioplasty and 4 months
after right cranioplasty.

290

Xenon CT was performed to measure cerebral blood
flow 3 days after the injury, before the left cranioplasty, after
the left cranioplasty (before the right cranioplasty), and after
the right cranioplasty. The cerebral blood flow at 3 days after
the injury was 18.7 ⫾ 12.3 mL/100 mL/min and 26.5 ⫾ 11.6
mL/100 mL/min in the left and right hemispheres, respectively (Fig. 4A). It was slightly increased to 26.1 ⫾ 19.5
mL/100 mL/min in the left hemisphere but remained the same
at 28.3 ⫾ 18.5 mL/100 mL/min in the right hemisphere at 8
months after the injury (just before the left cranioplasty; Fig.
4B). At 1 week after the left cranioplasty, it was 24.8 ⫾ 15.3
mL/100 mL/min and 34.8 ⫾ 20.3 mL/100 mL/min in the left
and right hemispheres, respectively (Fig. 4C). At 3 months
after the right cranioplasty, it had increased by approximately
2-fold to 36.4 ⫾ 23.2 mL/100 mL/min in the left hemisphere
and approximately 1.5-fold to 43.8 ⫾ 23.3 mL/100 mL/min
in the right hemisphere as compared with the levels obtained
3 days after the injury (Figs. 4D and 5).

DISCUSSION
SSFS is defined as a series of neurologic symptoms
with the skin depression at the site of cranial defect, which
develops several weeks to months after large external cerebral decompression. Yamaura and Makino1 and Yamaura et
al2 proposed SSFS in 1977 when they reported that some
patients with a depressed skin flap after external cerebral
decompression showed improved neurologic symptoms after
cranioplasty to correct tissue deformation under the flap.
SSFS is characterized by the rapid improvement of neurologic symptoms after cranioplasty.
The mechanism of SSFS has been considered to be as
follows: large cranial decompression is generally performed
to reduce high intracranial pressure, and the cranial defect
produced by craniotomy is directly affected by atmospheric
pressure; as cerebral swelling improves, the skin at the cranial
defect gradually sinks due to atmospheric pressure to deform
cerebral tissue, resulting in local cerebral circulation disorder
and cerebral dysfunction.3,4. However, few studies have reported SSFS. In particular, none has reported the change in
cerebral blood flow in patients with SSFS after cranioplasty,
as measured using xenon CT. The increased blood flow
observed in the present case may support the mechanism.
Xenon CT is a new diagnostic technique in which head
CT is performed under the inhalation of xenon gas to measure
cerebral blood flow by determining the concentration of
xenon in cerebral tissue.5,6. Estimation of cerebral blood flow
by noninvasive xenon CT has been used to identify bloodflow thresholds for the development of irreversible ischemia
following severe head injury or stroke. It is expected that
xenon CT technology will play a major role in severe head
injury or stroke research. The concentration in cerebral tissue
is color-coded on the monitor: the highest blood flow is
expressed in blue, followed by green and yellow, and the
© 2004 Lippincott Williams & Wilkins

Annals of Plastic Surgery • Volume 53, Number 3, September 2004

Sinking Skin Flap Syndrome

FIGURE 4. A, Xenon CT image taken 3 days after the injury and removal of hematoma by bilateral cranial decompression. The high
blood flow is expressed in light color and the low blood flow is expressed in dark color in this images. B, Xenon CT image before
left cranioplasty. C, Xenon CT image after left cranioplasty and before right cranioplasty. D, Xenon CT image after right
cranioplasty.
© 2004 Lippincott Williams & Wilkins

291

Isago et al

Annals of Plastic Surgery • Volume 53, Number 3, September 2004

FIGURE 5. Change in the cerebral blood flow. The flow was increased after the bilateral cranioplasty. Values are means ⫾ SD.

lowest blood flow is expressed in red. Regarding the change
in cerebral blood flow in the present case, as measured with
xenon CT, the cranioplasty of the left cranial defect alone
increased cerebral blood flow. The flow was further increased
after the cranioplasty for the right cranial defect was completed. These findings were consistent with the improvements
in her clinical symptoms. These results indicate that the
cerebral blood flow measurement using xenon CT can be a
good monitor for determining the effects of atmospheric
pressure on cerebral circulation at external decompression,
indication of cranioplasty, and prognosis of SSFS.
Conventionally, treatment of small cranial bone defects
caused by trauma or neurosurgery has involved autogenous
bone grafting of the outer layer of the cranium or the iliac
bone. For larger defects, resin still has been used for cranioplasty. However, the poor biocompatibility of the resin and
the occurrence of infection have frequently necessitated postoperative removal of the resin. In contrast, hydroxyapatite has
a high degree of biocompatibility and stability in vivo, and its
safety and effectiveness have been confirmed in animal experiments and in clinical settings. When performing cranioplasty on this case, the general condition of the patient is poor
and surgical invasion must be minimized. As demonstrated
here, procedures that use hydroxyapatite ceramic implants are
advantageous in such cases because operating times are short,
and patients quickly become ambulant because of the exclusion of bone harvesting.
Since cranioplasty has been discussed in terms of cerebral protection and improvement of appearance, it has been
considered that cranioplasty is not indicated in patients with
serious neurologic symptoms or in bedridden patients. However, cranioplasty may be useful for improving neurologic
symptoms and should therefore be performed in such patients.

292

CONCLUSIONS
This paper reports the case whose neurologic symptoms
of SSFS were improved by cranioplasty. The cerebral blood
flow of the present case, as determined using xenon CT, was
increased after cranioplasty. For SSFS cases, cranioplasty is
not only useful for cerebral protection and improvement of
appearance, but cranioplasty is also useful for improving
neurologic symptoms.

ACKNOWLEDGMENTS
We would like to extend deep thanks to Yoshio Takasato, MD, Director General of the Department of Neurosurgery, National Hospital Tokyo Disaster Medical Center, and
other staff physicians for their cooperation. We are grateful to
Lillian D. Traber for her assistance in the preparation of the
manuscript.

REFERENCES
1. Yamaura A, Makino H. Neurological deficits in the presence of the
sinking skin flap following decompressive craniectomy. Neurol Med.
1977;17:43–53.
2. Yamaura A, Sato M, Meguro K, et al. Cranioplasty following decompressive craniectomy: analysis of 300 cases. Neurol Surg. 1977;5:345–
353.
3. Nakamura T, Takashima T, Isobe K, et al. Rapid neurological alteration
associated with concave deformity of the skin flap in a craniectomized
patient: case report. Neurol Med. 1980;20:89 –93.
4. Stula D. The problem of the “sinking skin-flap syndrome” in cranioplasty.
J Maxillofac Surg. 1982;10:142–145.
5. Suzuki R, Nariai T, Hirakawa K. Measurement of cerebral blood flow by
stable xenon-enhanced computed tomography. Neurol Surg. 1993;21:
197–203.
6. Gur D, Good WF, Wolfson SK Jr., et al. In vivo mapping of local cerebral
blood flow by xenon-enhanced computed tomography. Science. 1982;
215:1267–1268.

© 2004 Lippincott Williams & Wilkins