Key-words:
Ascending transtentorial herniation - cranioplasty - subgaleal drainage
Introduction
Cranioplasties are regularly performed neurosurgical procedures that can be associated
with a variety of complications such as bone flap infection, seizures, and surgical
site hematoma in almost a third of patients.[[1]] However, most complications are readily amenable to treatment and seldom fatal.
One commonly practiced procedural step to reduce the risk of postoperative hematoma
accumulation is to place a closed negative-pressure subgaleal drain. We present a
patient with sinking skin flap syndrome (SSFS) that underwent a cranioplasty and subgaleal
drainage. She subsequently experienced immediate postoperative ascending transtentorial
herniation (ATH). Fewer than 30 cases of life-threatening subgaleal drain-related
complications have been documented. This case illustrates the importance of early
recognition of this rare phenomenon and intervention can be potentially life-saving.
Case Report
A 58-year-old female with a history of chronic rheumatic heart disease and atrial
fibrillation was admitted for cranioplasty. She previously underwent a decompressive
craniectomy for the management of her massive right middle and anterior cerebral artery
infarction 6 months before. The ischemic stroke rendered the patient severely disabled
with left hemiplegia and hemisensory loss. The patient also experienced chronic headache
and nonspecific dull aching pain over the left side of the body that required gabapentin
for partial relief. There was a large right fronto-parietal-temporal scalp concavity
coinciding with a craniectomy skull defect of 25 cm × 20 cm [[Figure 1]]a, [[Figure 1]]b, [[Figure 1]]c.
Figure 1: Preoperative computed tomography scan revealing a large sunken craniectomy site with
paradoxical herniation (a, b axial; c three-dimensional reconstruction). Immediate
postcranioplasty scan showing interhemispheric acute subdural hematoma (white arrow),
intraventricular hemorrhage (white arrowhead) and ascending transtentorial herniation
with upward displacement of the cerebellar vermis (grey arrow) (d, e, axial; f midsagittal).
One-day postoperative scan after subgaleal drain removal showing spontaneous resolution
of transtentorial herniation (g, axial; h, midsagittal)
Cranioplasty using the patient's autologous bone flap was performed uneventfully and
there was no intraoperative breach of the dura. Blood loss was 150 ml and the operation
lasted for 100 minutes. During scalp wound closure, a single subgaleal suction drain
was placed with vacuum applied as a routine measure. The drain was a negative pressure
closed system with an inner diameter of 3.33 mm (Fr 10) and according to the manufacturer
supplied medical device specifications, exerted a negative pressure 75 mmHg (10kPa).
Within 1 hour after extubation the patient developed status epilepticus with bilateral
eye deviation to the left. Pupil size was 3 mm bilaterally and reactive to light.
There was fast atrial fibrillation (160 beats/min) and hypotension of 85/40 mmHg.
At that juncture, the subgaleal drain output was <20 ml. The patient was mechanically
ventilated and her seizures were controlled after administrating intravenous midazolam
and phenytoin. A computed tomography (CT) brain scan showed an interhemispheric acute
subdural hematoma, intraventricular hemorrhage within the left occipital horn of the
lateral ventricle with obliteration of the quadrigeminal and superior cerebellar cisterns.
There was also upward displacement of the vermis at the level of the incisura and
flattening of the posterior third ventricle [[Figure 1]]d, [[Figure 1]]e, [[Figure 1]]f. The patient was diagnosed with ATH and the subgaleal drain was immediately removed.
She was sedated for 24 hours and a CT brain performed the next day showed resolution
of the ATH [[Figure 1]]g, [[Figure 1]]h. The patient eventually recovered to her preoperative functional performance level
with no further headaches and resolution of her limb numbness. There were no seizures
and her phenytoin was weaned off a month after the cranioplasty.
Discussion
The term “SSFS” was first introduced in 1977 by Yamaura and is synonymous with the
“syndrome of the trephined” that exclusively affects craniectomy patients.[[2]] The clinical presentation is protean ranging from chronic fatigue, headache, and
dizziness to more disabling symptoms such as cognitive decline, seizures, visual disturbances,
speech, and sensorimotor deficits.[[3]] The exact incidence is unknown, but from a prospective cohort study of patients
with malignant middle cerebral artery syndrome who underwent hemicraniectomy 26% experienced
SSFS 5 months after the procedure.[[4]] There are no diagnostic criteria, but a characteristic feature of SSFS is the reversibility
of symptoms after cranioplasty and this has led to greater understanding of its possible
pathophysiology.[[5]] The syndrome is believed to develop when atmospheric pressure exceeds intracranial
pressure and in extreme cases can manifest as paradoxical herniation. The paradox
lying in the fact that herniation occurs in the absence of intracranial hypertension.
The consequences of atmospheric pressure exertion on a large craniectomy site can
be far reaching. Not only is there direct brain compression but also a global disruption
of cerebrospinal fluid (CSF) hydrodynamics with regional reductions in microarterial
and venous outflow circulation.[[3]] Cranioplasty has been shown to elicit significant improvements in cerebral perfusion
by xenon-133 CT; glucose metabolism by fluorodeoxyglucose-18 positron emission tomography;
and systolic craniocaudal CSF flow velocities by dynamic phase-contrast magnetic resonance
imaging.[[4]],[[5]],[[6]] In spite of the benefits of cranioplasty, there have been sporadic reports of postoperative
hemorrhagic stroke or diffuse cerebral edema (DCE or pseudohypoxic edema) attributed
to the rapid increase in cerebral blood flow following reexpansion of fragile damaged
brain tissue with impaired vascular autoregulation.[[7]],[[8]],[[9]],[[10]] We suspect that the additional application of negative pressure drainage in our
patient may have aggravated luxury hyperperfusion injury as exemplified by the presence
of subdural and intraventricular hemorrhage.
From the year 2000–2017, 25 patients, including the present case, have been reported
to develop severe cardiovascular changes, DCE, or intracranial hemorrhage attributable
to negative-pressure drainage [[Table 1]]. Most patients had preceding SSFS and experienced drain-related complications after
cranioplasty regardless of the presence of a CSF shunt. Two developed severe intracerebral
hemorrhage secondary to tearing of the superior sagittal sinus and even intracranial
aneurysm rupture after an otherwise uneventful craniotomy.[[12]],[[15]] An overwhelming majority of these cases were fatal and neurological deterioration
usually occurred within 3 hours after the operation.
Table 1: Characteristics of patients with postcranioplasty/craniotomy negative-suction subgaleal
drainage-related complications
Table 1: Contd...
Ever since Georges Dieulafoy's 1873 seminal treatise on the merits of “pneumatic aspiration”
in the management of wounds, the placement of drains has dominated surgical practice.[[26]] In his treatise, Dieulafoy cautioned that “the operator must be condemned who makes
use of aspiration without understanding.”[[26]],[[27]] The induction of acute intracranial hypotension by subgaleal drains can result
in catastrophic outcomes.[[11]],[[12]],[[13]],[[14]],[[15]],[[16]],[[17]],[[18]],[[19]],[[20]],[[21]],[[22]],[[23]],[[24]],[[25]],[[28]],[[32]] Our patient likely experienced ATH when vacuum suction to the supratentorial compartment
was applied. The immediate clamping of the subgaleal drain with subsequent recovery
of the patient's consciousness and stabilization of vital signs supports this theory.
ATH, also known as reverse or upward coning, is the least frequently encountered of
brain herniation syndromes. It is generally triggered by the abrupt supratentorial
decompression of obstructive hydrocephalus secondary to cerebellar mass lesions in
65% of cases.[[29]] The precipitous plunge of supratentorial compartment pressure establishes a steep
gradient that displaces the anterior lobe and vermis of the cerebellum superiorly
through the tentorial incisura. Subsequent brainstem compression and compaction of
the basal veins could cause life-threatening hemorrhagic venous infarction. Early
signs of ATH include somnolence, cardiovascular collapse, arrhythmias (either bradycardia,
atrial, or ventricular fibrillation), and pinpoint pupils.[[2]],[[3]] A high-index of suspicion is required for this uncommon phenomenon and is potentially
reversible if recognized early. This is the first documented case of ATH occurring
after cranioplasty, but it is believed that previous cases of severe bradycardia and
arterial hypotension encountered during subgaleal drain placement may have been due
to the rostral shift of trigeminal or vagal brainstem nuclei.[[13]],[[14]],[[17]],[[19]],[[32]]
To demonstrate the degree of intracranial compartment pressure changes created, researchers
have noted that intracranial pressure in the contralateral hemisphere can drop expeditiously
to -20 mmHg at the moment of drain vacuum suction.[[11]] Furthermore, an experimental study of three commonly used closed drainage systems
discovered that significantly high negative pressures, in excess of -150 mmHg and
beyond physiological intra-arterial pressure, could be generated.[[27]] In contrast, there is little evidence to support the prophylactic use of closed
suction drainage and its adoption is typically founded on anecdotal experience.[[27]],[[30]],[[31]] Only two retrospective cohort studies of supratentorial craniotomy patients were
performed and both failed to demonstrate their efficacy in preventing postoperative
epidural hematoma.[[30]],[[31]]
This case illustrates the risks of routine negative-pressure subgaleal drainage during
cranioplasty for patients with suspected SSFS. To avoid this complication, we recommend
refraining from drain placement by conducting meticulous hemostasis, and if considered
necessary, withholding vacuum application until after the cranioplasty. Alternatively,
one may dispense with suction altogether and allow drainage to occur passively by
gravity although the efficacy of such a measure remains unknown.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form the patient(s) has/have given his/her/their consent for his/her/their
images and other clinical information to be reported in the journal. The patients
understand that their names and initials will not be published and due efforts will
be made to conceal their identity, but anonymity cannot be guaranteed.
