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Year : 2015  |  Volume : 63  |  Issue : 6  |  Page : 895--902

Four-quadrant osteoplastic decompressive craniotomy: A novel technique for refractory intracranial hypertension - A pilot study

Anil Kumar Peethambaran1, Vinu V Gopal1, Jiji Valsalamony2,  
1 Department of Neurosurgery, Government  Medical College, Trivandrum, Kerala, India
2 Department of Imageology, Regional Cancer Center, Trivandrum, Kerala, India

Correspondence Address:
Anil Kumar Peethambaran
House No  12, Avittom Road, Medical College  (PO), Trivandrum  -  695  011, Kerala


Background: Decompressive craniectomy (DC) with duroplasty is the gold standard for refractory intracranial hypertension despite paucity of randomized controlled trials. There are several morbidities associated with DC of which the persistence of bony defect is of paramount importance. Studies have shown that many of the morbidities associated with DC get reversed following replacement of the bone flap. Aim: To design a novel technique for control of refractory intracranial pressure (ICP), as well as to study its safety and efficacy compared to the conventional DC technique. Material and Methods: We conducted a prospective, comparative, observational pilot study comparing four-quadrant osteoplastic decompressive craniotomy (FoQOsD) with conventional DC. The demographic features, postoperative variables such as operating time, number of days of intensive care unit (ICU) stay and survival, as well as radiographic variables such as change in the midline shift (MLS) and expansion of the compressed brain were analyzed using relevant statistical tests. Results: Twenty patients were selected and grouped into two groups of 10 patients each. The male: female ratio in the two groups were 8:2 and 7:3, respectively, and the mean age at presentation was 42.7 ± 1.45 years in the FoQOsD group and 43.6 ± 1.32 years in the DC group. Both the groups were comparable in relation to the duration of surgery, duration of ICU stay, and survival (P > 0.05). There was significant brain expansion and reversal of MLS (P < 0.001) in the FoQOsD group, factors which were comparable to that in the DC group. Conclusions: FoQOsD may be as effective as conventional DC in managing intracranial hypertension. This procedure mainly avoids a revision cranioplasty. A prospective randomized controlled trial with a large sample size may be initiated for obtaining more accurate data.

How to cite this article:
Peethambaran AK, Gopal VV, Valsalamony J. Four-quadrant osteoplastic decompressive craniotomy: A novel technique for refractory intracranial hypertension - A pilot study.Neurol India 2015;63:895-902

How to cite this URL:
Peethambaran AK, Gopal VV, Valsalamony J. Four-quadrant osteoplastic decompressive craniotomy: A novel technique for refractory intracranial hypertension - A pilot study. Neurol India [serial online] 2015 [cited 2022 Oct 6 ];63:895-902
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Decompressive craniectomy (DC) with duroplasty is the gold standard for refractory intracranial hypertension despite paucity of randomized controlled trials.[1],[2],[3] There are several morbidities associated with DC of which the persistence of bony defect is of paramount importance.[4],[5],[6] Studies have shown that many of the associated morbidities get reversed following replacement of the bone flap.[7],[8],[9] Hence, we introduced a novel technique of "four-quadrant osteoplastic decompressive craniotomy (FoQOsD)," which is mainly aimed at avoiding a second surgery of revision cranioplasty, and, thus, helps in reducing the economic burden, as well as in preventing the morbidity of the bone defect. In this pilot study, we compared FoQOsD with the conventional DC as well as other bone flap preserving techniques.[10],[11]

 Materials and Methods

We conducted a prospective, comparative, observational pilot study comparing the technique of FoQOsD with that of the conventional DC in bringing about lasting relief of intracranial pressure. A total of 20 patients were selected as per the selection criteria described below. The selected cases were divided into two groups of 10 patients each. Group 1 included patients undergoing the FoQOsD and Group 2 included patients undergoing the conventional DC. All patients were treated at a single institution (Neurosurgical Ward, Government Medical College, Trivandrum). All patients underwent routine preoperative investigations, and after obtaining informed written consent, were taken up for the surgical procedure. Approval was obtained from the Institutional Review Board for recruiting these patients for the study. The patients recruited for the new technique were from the first unit of neurosurgery (Government Medical College, Trivandrum) with supervision of the senior surgeon; the control group were patients taken from the second unit.

Selection criteria

The inclusion criteria included age between 15–65 years; a Glasgow Coma Scale (GCS) ≤8; serial computerized tomography (CT) of the head showing features of raised intracranial pressure (ICP) that included a mid-line shift (MLS) >5 mm and compressed cisterns; a fall in GCS of ≤2 points (associated with radiological features stated above) from the time of the initial presentation; and, intraoperative tense brain after the hematoma evacuation.

The exclusion criteria included a GCS = 3, bilateral fixed and dilated pupils; severe coagulopathy; signs of brainstem involvement; and, penetrating brain injury.

The demographic and baseline characteristics are shown in [Table 1]. All patients were treated according to the American Association of Neurosurgeons' guidelines for management of severe head injury.{Table 1}

Surgical technique

Incision and cranial exposure

The patient was placed in supine position, with the head turned to the opposite side with the head end elevated. The procedure was performed under general anesthesia. The skin incision was the standard reverse question mark incision 1 cm in front of the tragus, extending above and behind the ear to approximately the posterior mastoid line and then carried forward to within 1 cm from midline to end at or near the hairline [Figure 1]a.{Figure 1}

Bone work

This was similar to the conventional DC flap with an additional burr hole at the center. The portion of the bone flap removed is shown in [Figure 1]b,[Figure 1]c,[Figure 1]d. The temporal craniectomy extended to the floor of the middle cranial fossa up to the level of the zygomatic arch. The bone flap was then divided into four-quadrants beginning from the central burr hole after cutting the periosteum. We used either a drill with a craniotome attachment or a Gigli wire. Then, the periosteum on each bone piece was sutured loosely to other pieces, as well as to the periosteum on one side of the calvarium with prolene/silk sutures, as shown in [Figure 1]c,[Figure 1]d,[Figure 1]e,[Figure 1]f, [Figure 2]c, and [Figure 2]d.{Figure 2}

Dural opening

The dura was opened in a cruciate fashion. A synthetic dural patch was kept tucked under the original dura over the brain surface to prevent the brain from bulging out [Figure 1]e.

The bone flap with four pieces loosely connected by the periosteum was carried over the durotomy site and sutured to the opposite side [Figure 1]f, [Figure 2]f and [Figure 3]. Soft tissue closure was done in two layers.{Figure 3}

As the brain expanded, the bone flaps floated out in all four different directions giving space for the expanding brain thereby reducing the ICP [Figures 1g and 3]. The patients were monitored in the ICU until their discharge from the hospital. The complications occurring during both the procedures (DC and FoQOsD) were recorded.

Representative case

A 24-year-old man, following a road traffic accident, presented with an acute subdural hematoma of 1 cm thickness and 12 mm mid-line shift. He underwent a FoQOsD [Figure 2]a,[Figure 2]b,[Figure 2]c,[Figure 2]d,[Figure 2]e,[Figure 2]f. His postoperative scans showed significant reduction in the MLS. The preoperative and postoperative CT scans of this patient who underwent a FoQOsD craniotomy are represented in [Figure 4]a,[Figure 4]b,[Figure 4]c,[Figure 4]d. The preoperative and postoperative CT scans of a conventional DC are presented for comparison in [Figure 5]a and [Figure 5]b. The final external appearance of the patient 3 months after the FoQOsD craniotomy was comparable to that of the patient who underwent the conventional DC [Figure 6]a and [Figure 6]b. The patient was followed-up for a period of 6 months, following which a near normal alignment of the skin bone flap with good evidence of bony fusion was obtained [Figure 4]d.{Figure 2}{Figure 4}{Figure 5}{Figure 6}

Statistical analysis

Data were collected in a prewritten proforma and entered in Microsoft Excel spreadsheet and analyzed using Statistical Package for Social Sciences (SPSS Inc. Released 2007. SPSS for Windows, Version 16.0. Chicago). Clinical and radiographic characteristics were compared between the novel technique and the conventional DC group. The continuous response variables were presented by mean ± standard deviation, and t-test was applied to compare the means between the two groups. Categorical data were analyzed using Chi-square test with a P < 0.05 taken as significant. Moreover, wherever necessary, nonparametric tests were also applied. If the data were not normally distributed, Mann–Whitney test was used to compare the two groups and Wilcoxon test was used to compare within the two groups. Two tailed significance was kept at <0.05.

Data analysis

Clinical status

The patient demographics included age, sex, indications for surgical decompression, laterality of the lesion, and GCS score. The postoperative clinical variables included operating time, need for reoperation, need for and duration of ventilation, the number of days of ICU stay, and patient outcome.

Radiological findings

Both the immediate and serial postoperative CT scans were reviewed. The change in MLS [Figure 7]a and percentage of brain expansion on the ipsilateral and the contralateral side were compared between the two groups [Figure 7]a and [Figure 7]b.{Figure 7}



A total of twenty patients were selected for the study and their numbers were divided into two groups of 10 patients each. The male: female ratio in the two groups were 8:2 and 7:3, respectively, and the mean age at presentation was 42.7 ± 1.45 in the FoQOsD group and 43.6 ± 1.32 in the DC group. The main indication for decompression for majority of the cases included trauma with an associated subdural hematoma; intracerebral hematoma formed the second most frequent indication [Table 1]. There were no statistically significant differences among any of the demographic variables including the patients' age, surgical indications or the site of decompression (P > 0.05) [Table 1].

Postoperative outcome

Both the two groups were comparable in terms of the operating time, the duration of ICU stay and survival (P > 0.05) [Table 2]. The mean operating time in the FoQOsD group was more than that of the conventional technique by seven minutes, which was not statistically significant (P = 0.674). Our case series showed a high mortality rate of 70% in the FoQOsD group and 50% in the DC group. There was no significant difference between the two groups in terms of percentage survival (P = 0.361) [Table 2]. The Glasgow Outcome Score in the FoQOsD group showed that seven patients died and three patients survived among whom one patient had a good recovery and two patients had a moderate disability at a 6 month follow-up. One patient in the FoQOsD group required re-exploration and removal of the bone flap because of expansion of the hematoma. There was an observed improvement in the Glasgow Coma Scale (GCS) score in the FoQOsD group [Figure 8] though not statistically significant by the Mann–Whitney test (P = 0.55). Postoperative median interquartile range in the FoQOsD group was 12.0 (10.75–12.5) compared to 11.5 (11–12) in the conventional DC group [Figure 8]. On comparing the two groups in terms of percentage change in the GCS score by Wilcoxon test, no statistically significant differences were detected [Table 2]. The number of days of ICU stay was 21.3 ± 11.1 in the FoQOsD group and 21.7 ± 6.7 days in the DC group. Surgical site infection following the conventional DC was 30% in the conventional DC group and 20% in the FoQOsD group. On comparing the two groups, neither the duration of hospital stay nor infection rates showed statistically significant differences (P = 0.924). In the FoQOsD group, 33% patients developed hydrocephalus compared to 40% patients in the DC group who survived. None of the patients in the FoQOsD group had acute neurological deterioration due to bone flap sinking onto the brain once the brain swelling had subsided.{Table 2}{Figure 8}

Radiological variables

The immediate postoperative CT scan showed that patients had a significant reversal of MLS compared to the preoperative value in both the groups as assessed by paired t-test (P < 0.001) [Table 3]. There was no significant difference between the two groups in terms of percentage change in MLS by independent sample t-test (P = 0.257) [Table 3]. The expansion of the compressed contralateral side, as well as the ipsilateral side, showed significant change as measured by the mean brain width on the postoperative CT scan in both the groups (P < 0.001) [Table 3]. Brain expansion using the new technique was proportional to that obtained using the conventional DC. On comparing the two groups by paired t-test, there was no statistically significant difference between the groups in terms of percentage change in brain width on ipsilateral and contralateral side of the decompression (P = 0.371 and P = 0.134, respectively) [Table 3].{Table 3}

Thus, the results showed that the novel technique of FoQOsD was equally effective and comparable to the conventional technique of DC.


The management of intracranial hypertension is often the greatest challenge for a neurosurgeon. In approximately 10–15% of cases, intracranial hypertension is refractory to medical management.[1],[12] In such cases, DC is a lifesaving procedure as it is effective in lowering the ICP to below 20 mm of Hg in 80% of the cases.[13],[14],[15]

However, DC is associated with a varied spectrum of complications because of absence of a bone flap.[16],[17],[18] The main complications that may occur following a DC include vulnerability of the underlying brain to direct injuries due to the loss of bone, the need for a second surgery to perform a cranioplasty, and a higher incidence of infection, hydrocephalus, syndrome of the trephined, intracerebral hematoma, delayed seizures, cerebrospinal fluid leak (3–5%), extra-axial collection (both epidural [20%], and subdural [5%]).[7],[16],[17],[19],[20],[21] Studies have shown that many of these morbidities get reversed following replacement of the bone flap.[7],[8],[9] With regard to the timing of cranioplasty, studies have shown that patients with an early cranioplasty had a better functional outcome.[22],[23],[24] Hence, every effort should be made to reduce these specific complications associated with the absence of a large area of the bone flap. We believe that our new technique provided adequate compliance to the brain (as has been achieved in DC) and was also effective in reducing the above mentioned complications.

Infection rates following a DC and cranioplasty ranged from 3–7%.[16],[17],[25] Based on a review of literature, the greatest risk of infection was associated with revision cranioplasty with a stored bone flap.[25] Storage of bone in a freezer for prolonged periods before reimplantation increases the risk of infection.[26] Thus, our procedure, where the bone flap was reposited in its original place at the time of initial decompression avoided these complications. The incidence of surgical site infection rate in the FoQOsD group was comparable to that found in the conventional DC group in our study.

The reported incidence of posttraumatic hydrocephalus in patients who underwent a DC was 20.7%.[27] The proposed mechanism of hydrocephalus was perhaps the obstruction of arachnoidal granulations by the surgical debris and inflammation.[28] If this supposition is true, an early cranioplasty should restore the normal ICP dynamics leading to spontaneous resolution of hydrocephalus.[28] However, a FoQOsD flap will not completely prevent the development of hydrocephalus as it also offers minimum resistance to brain expansion in the initial phase, as seen in DC. In our study, 3 out of 10 patients survived in the FoQOsD group. One of them had hydrocephalus which is comparable to the three patients in the conventional DC group who developed hydrocephalus. Other types of flap preserving surgeries [10],[11],[29] have not addressed this issue as they do not have a long-term follow-up.

The syndrome of the trephined (the sinking flap syndrome) is a delayed complication that is associated with headache, dizziness, irritability, memory problems, and mood disturbances.[30] The proposed mechanism is that since there is no bony support, atmospheric pressure is directly transferred onto the surface of the brain. Neurological worsening has been described after DC with improvement occurring following institution of a cranioplasty.[7] Several studies have shown that these deficits are usually reversible and resolve following the performance of a cranioplasty.[22],[23],[24] None of the patients in either group had acute neurological deterioration due to bone flap sinking on the brain once the swelling subsided. FoQOsD prevents the syndrome of the trephined as the bone flap effectively gradually returns back to its normal position along with the regressing brain.

The removal of the bone flap leads to loss of tamponade effect facilitating hematoma expansion on both the ipsilateral and contralateral side.[13] Two out of the ten patients in the conventional DC group showed an increase in size of the residual intracerebral hematoma. Only one patient in the FoQOsD group showed hematoma expansion and required a reexploration.

Subdural effusion has been reported following a DC.[21] Extra-axial collection in the subdural space was seen in 50% of patients who underwent a FoQOsD and in 40% patients who underwent a conventional DC. All these patients only required conservative management. None of the patients in either group developed CSF leak.

Postoperative seizures were seen in 20% patients in the FoQOsD group and 30% patients in the conventional DC group. The relatively lesser incidence of seizures in the FoQOsD group may be due to the uniform external herniation of brain that does not lead to additional brain damage. This complication has not been well addressed in the literature reporting the results of hinge craniotomy and floating resin cranioplasty. All these results show that patients in the conventional DC group are comparable in terms of their postoperative morbidities.

Our case series shows a high mortality rate of 70% in the FoQOsD group and 50% in the DC group. The higher mortality rate in our study may be because the majority of our enrolled patients sustained polytrauma and had a previous medical illness. The percentage survival in similar studies that utilized a "hinge craniotomy"[11] and a "floating resin cranioplasty"[10] were 52% and 86%, respectively. The higher percentage survival in both the studies may have been because the patients enrolled included more stroke patients rather than those who sustained traumatic brain injury with polytrauma.

An ideal procedure for refractory intracranial hypertension should be the one that effectively decompresses the brain and limits the associated morbidity. We designed a novel technique that combines the effect of adequate cranial decompression and avoids a second surgery to replace the bone flap later on. In our study, a repeat CT scan showed the return of MLS toward normalcy, which can be considered as a measure of reduction in the ICP.[31] We found this procedure cost effective as no implants were used. This procedure also prevented the physical and psychological morbidity of a bone defect. With regression of brain swelling, the bone flaps gradually returned to their normal anatomical position. The procedure, therefore, provided a reasonable cosmesis, and also reduced the vulnerability of the underlying brain to external injuries.

Compared with a hinge craniotomy, our procedure provided lesser resistance for the brain to expand. Brain usually bulges out in a hemispheric pattern out of the calvarial defect. The bone pieces in our procedure fan out in four different directions offering minimum resistance to the brain, whereas in hinge craniotomy and floating resin cranioplasty, the expanding brain is offered resistance to a certain extent by the presence of the bone flap directly over it. This concept is illustrated in [Figure 9].{Figure 9}

Our greatest limitation was that measurement of ICP could not be performed. Proper randomization was not done in our cases considering the emergent nature of the situation in which the surgery was performed. Inter group variability in terms of demographic characteristics and variability in the site and extent of intracranial lesions is another limitation.


FoQOsD may be as effective as the DC technique in the surgical management of refractory intracranial hypertension. The major advantage of this procedure was that it avoided a second surgery of a revision cranioplasty. FoQOsD also avoided the economic burden of a second surgery, and the psychological morbidity due to the presence of a large bony defect. It also avoided the syndrome of the trephined. In our study, we have addressed the issue of expansion of the effaced brain on both sides of decompression along with dealing effectively with the MLS, which makes this study more relevant. A prospective randomized controlled trial with a large sample size may be initiated for obtaining accurate results.


I would like to thank my colleagues in the Department of Neurosurgery, Medical College, Trivandrum.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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