Basal Cisternostomy - A Microsurgical Cerebro Spinal Fluid Let Out Procedure and Treatment Option in the Management of Traumatic Brain Injury. Analysis of 40 Consecutive Head Injury Patients Operated with and without Bone Flap Replacement Following Cisternostomy in a Tertiary Care Centre in India
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.314535
Source of Support: None, Conflict of Interest: None
Keywords: Basal cisternostomy, cerebral oedema, decompressive craniectomy, neurotrauma, traumatic brain injuryKey Message: Basal Cisternostomy is an effective micro surgical procedure to be considered seriously in the surgical management of traumatic brain injury patients in order to better the existing overall outcome data.
Traumatic Brain Injury (TBI) is the most devastating disease that occupies most of the neurosurgical practices in Asia due to sheer size of the population and growing road traffic accidents. Many patients are left with severe morbidity in spite of advanced neuro critical care. Decompressive Craniectomy (DC) has been the sole and most popular neurosurgical procedure performed on majority of severe TBI patients with severe brain oedema that is refractory to medical management. Though a wide DC has shown to reduce intra cranial pressure (ICP), in reality it does not reduce the oedema but provides an outlet for the oedematous brain tissue to expand. The increasing incidences of side effects of DC has opened a wide arena to find alternative techniques to avoid or prevent removal of bone flap after dural decompression and evacuation of clots and contusions.
Basal Cisternostomy (BC) is an emerging microsurgical technique in the management of cerebral oedema in TBI. By this technique, CSF is let out from basal cisterns which reduces cerebral oedema and relaxes the brain in acute and subacute settings thus allowing replacement of bone flap in otherwise irreplaceable settings. This technique has gained popularity in the last decade and many neurosurgeons are now performing this technique of CSF let out in TBI.,,
We analysed all our initial cases and brought out the results for the first time in Indian literature and also discussed in detail the rationale for recommending this procedure.
A total of 40 patients underwent Basal Cisternostomy in TBI, admitted in the senior author's unit, between January 2016 and April 2019. All surgeries were performed by a single surgeon (Senior Author) with microsurgical expertise. Demographic data and data regarding patient condition and management were collected from hospital records. The data collected included age, sex, GCS at admission, duration of preoperative ventilation, duration between injury and surgery, status of bone flap, duration of postoperative ventilation and duration of hospital stay. Radiological information was collected from Picture Archiving and Communication System (PACS). Outcome was assessed using a telephonic questionnaire or follow-up visits using Glasgow outcome scale (GOS). Results were analysed separately for all grades of injury and compared using SPSS (Statistical Package for Social Science) software.
All TBI patients admitted in our center were initially evaluated and managed according to standard protocols. Those patients who needed immediate surgery for progressive neurological deterioration or impending coning were taken up for surgery immediately. Patients with GCS – 3/15 in combination with dilated and fixed non reacting pupils, absent or inadequate spontaneous respiration, cardiopulmonary instability, delayed admission following trauma with above clinical status, scans showing infarcts of brainstem, ground glass appearances with gross midline shifts and multi organ injuries with profound hypotension were not subjected for surgery. Other patients were managed in ICU (Intensive Care Units) with continuous ventilation and anti-oedema medications hyperventilated for short period as needed and assessed periodically for clinical status to be taken up for surgery when needed. We have not used Intra Cerebral Pressure (ICP) monitoring and all decisions for continuing medical management and surgical intervention were taken with clinical and radiological assessments.
During surgery patient is positioned with head in slight extension to avoid undue retraction of frontal lobe while opening the basal cisterns. Adequate craniotomy, drilling of lesser wing of sphenoid and bony decompression is done depending on the location of cerebral injury or hematoma. Subsequently after evacuation of clots and contusions if any, CSF is let out of the basal cisterns through the optico-carotid, lateral carotid cisterns and by opening Liliequist membrane, reaching pre pontine and infra tentorial cisterns. Thorough saline wash ensures satisfactory removal of subarachnoid blood. A small drain is placed in the cistern and brought out of the wound for drainage of CSF in postoperative period. Subsequent to satisfactory CSF removal the brain relaxes in most of the cases providing sufficient space to replace the bone flap. CSF drainage is limited to 100 to 150 ml per day by keeping the drainage bag at the level of the head for 5 to 7 days. The patients are clinically assessed and data recorded.
The mean age of the patient population was 44 years. There were 31 male and 9 female patients with a male to female ratio of 3:1. The mean GCS (Glasgow Coma Scale) at admission was 7. Majority of patients operated had a severe head injury constituting 29 (72.5%) patients while 8 (20%) had moderate head injury and 3 (7.5%) had mild head injury. The mean duration of preoperative ventilation was 21 hours while the mean duration between injury and surgery was 31 hours. 27 (67.5%) patients underwent Basal Cisternostomy alone (BC) where bone flaps were replaced while 13 (32.5%) patients underwent Decompressive Craniectomy and Basal Cisternostomy (DC + BC) with bone flap removed [Table 1].
The mean GCS at discharge was 13. The mean Glasgow outcome scale (GOS) at 6 months follow up was 4. Thirty-three (82.5%) patients had a favourable outcome (GOS of 4 to 5) while five (12.5%) patients had an unfavourable outcome (GOS 2 to 3) and two patients had expired with a mortality rate of 5%.
Patients were analysed separately for outcome in both BC group and DC + BC group and compared. BC group had a greater beneficial effect for moderate and mild head injury with 100% favourable outcome. In severe head injury patients DC + BC group had no significant advantage statistically over BC group with favourable outcome of 72.7% and 77.8% in the two groups respectively. [Table 2] Complications encountered were wound infection due to CSF leak in two (5%) patients and hydrocephalus in five (12.5%) patients.
The mean duration of postoperative ventilation was 11 days and the mean duration of hospital stay was 41 days. Preoperative ventilation of less than 3 hours had a 100% favourable outcome in both groups. In patients who had longer period of ventilation, favourable outcome was noted as 82.3% in BC group and 66.6% in DC + BC group. Factors that determined longer period of ventilation were unstable patients with severe brain oedema. On analysing the severe head injury group patients separately, similar results were depicted in regards to ventilation. [Table 3] and [Table 4].
Patients operated earlier showed better results than those who got operated later from the time of injury irrespective of severity of neurological status. [Table 5] and [Table 6].
CSF let out procedures
Supported by Class 3 studies CSF drainage in the form of External Ventricular Drainage (EVD) has been included as a separate topic in the fourth edition of Brain Trauma Foundation guidelines in the management of severe traumatic brain injury. This initiation has signified the value of CSF drainage in the reduction of cerebral oedema. In general CSF can be let out from convexity sulci, sylvian cisterns, basal cisterns and lateral ventricles. Opening sulcal and sylvian cisterns is difficult in severely oedematous brain. Ventricular tapping is often difficult to attempt in oedematous brain as ventricles are small and squashed due to midline shift and herniation. Though ventricular tapping lets out CSF from the ventricles it defies logic when done on dilated ventricles found usually opposite to midline shift that may further aggravate brain shift.
Basal Cisternostomy means opening subarachnoid cisterns at base of the brain and letting out CSF from them. Basal cisterns are classified as supra tentorial and infra tentorial cisterns separated by Lileiquist arachnoid membrane.
In this procedure basal cisterns are reached through a subfrontal or pterional approaches. Arachnoid layers are opened at optico-carotid, inter optic and lateral carotid corridors to open the cisterns. Further dissection through optico carotid and lateral carotid corridor, the Lileiquist membrane is reached and perforated and opened to access pre pontine cisterns. CSF is drained from both supra and infra tentorial basal cisterns with copious saline irrigation. A drain tube placed at pre pontine and brought out through the corridor that would facilitate CSF drain in postoperative period [Figure 1]. Even in severe oedematous brain it is possible to perform cisternostomy after removing subdural, intra cerebral haematomas and contusions. Adequate drilling of lesser wing of sphenoid is sufficient and rarely anterior clinoidectomy helps in reaching the infra tentorial cisterns as recommended by Iype et al. However in our experience since we perform sphenoid ridge excision in most cases, the need for clinoidectomy was never experienced.
Subsequent to satisfactory let out of CSF, the brain becomes relatively lax in majority of severely oedematous brain and in all most in all cases of moderately oedematous brain [Figure 2]a and [Figure 2]b. Dural approximation and floating bone flap replacement was possible in most of these cases. In malignant oedematous brain where the cortical surface prolapses beyond the outer table it was impossible to replace the bone flap in spite of CSF drain. In these cases the CSF was usually thick, mixed with blood and volume of CSF let out was also minimal. Outcome of such cases were found to be very poor. Hence to a large extent a relaxed brain and the possibility of replacement of bone flap following cisternostomy denotes good prognosis and is a predictable sign for favourable outcome, while inability to replace bone flap prognosticate bad result [Figure 3]a, [Figure 3]b, [Figure 3]c.
Basal cisternostomy is technically much easier in a well-ventilated patient than in non ventilated or improperly ventilated patients preoperatively. Cellular oxygenation is essential in preventing secondary cellular injury due to hypoxia especially during transport from accident site or while shifting from one hospital to another. In most of our patients we prefer to asses clinical status, ventilate adequately along with anti-oedema measures, and repeat CT brain to assess brain oedema and then subsequently subject the patients for surgery as needed.
As we all know while CSF drainage reduces cerebral oedema, the mechanism how it achieves relaxation of brain is widely discussed and debated in world literature and in neurosurgical forums. Certainly CSF drainage effectively relaxes the brain by reducing its volume in the system. This observation kindled many neurosurgeon's brain and opened up many questions to be answered. Does release of locked up CSF in cisterns and Virchow Robin's spaces alone resulted in a lax brain or any other mechanism that existed, are yet to be understood.
Iype et al. have proposed a hypothesis called 'CSF Shift Edema' as the cause of cerebral edema following head injury and its reversal with CSF let out by performing cisternostomy. This hypothesis was postulated following the understanding of research works done by Bulat, Oreskovic and Klarica. It is explained that diffuse subarachnoid hemorrhage following head injury at basal cisterns lock up the CSF in the subarachnoid cisterns and in the Virchow Robin's space (VRS -the final channels) that is in continuity with cisterns under great pressure. The CSF diffuses in brain parenchyma in extracellular space from VRS thus causing cerebral oedema. Research works have proved close contact of CSF in VRS and interstitial spaces in brain tissue through Glymphatic pathways and by demonstrating transit of fluid in the brain tissue. Illif et al. demonstrated CSF entering brain parenchyma through VRS in animal models using two-photon microscopy and by injecting fluorescent tracers in cisterna magna., Reversal of locked up CSF from VRS help in reducing brain oedema. In-depth reading of these research works and understanding of the CSF dynamics may provide an opportunity to appreciate the proposed hypothesis.
This hypothesis became the rationale behind using Cisternostomy in managing cerebral oedema in TBI. It was initially introduced by Iype in 2006 and later followed by Roy Thomas Daniel (Swiss 2015), Younghong Wang (China 2017) and by the senior author (India 2016) as a regular procedure in head injury management. Ever since Kocher described DC procedure, it has been the standard of care for patients with severely oedematous brain . Analysis of DC also has brought out its limitations and side effects that it has produced such as bulging brain tissue outside the calvarium and resultant cortical fiber tractions, strangulations, venous engorgements during the initial period and sunken flap syndromes at later date resulting in delayed or no recovery. Also there is always a need for second surgery for replacing the bone flaps that apart from measures to preserve the bone flaps and resultant cost factors to the patient. Management of these sequelae itself is a daunting task for many surgeons who practice DC as a routine procedure. The popular DECRA trial and RESCUE trials that analysed the clinical outcomes following DC concluded that it increased the incidence of vegetative state and severe disabilities in spite of it effectiveness in reducing the ICP. The Brain Trauma Foundation fourth edition has recommended a large fronto tempero parietal (FTP) of more than 15 cms to smaller and inadequate decompressions to achieve effective result.
Analysis of result
Our analysis shows satisfactory results with basal cisternostomy in severe head injury patients with a favourable outcome of 77.8% in BC group (Basal cisternostomy alone) and 72.7% in DC + BC group (Decompressive Craniectomy with Basal Cisternostomy) groups with a mortality of 6.8% in the severe traumatic brain injury group. The outcome as well as mortality in this group is comparable and better than Decompressive Craniectomy results from other studies. While Cooper et al. reported 30% favourable outcome and 19% mortality with DC, Jiang et al. reported 28.6% favourable outcome with large craniectomy and surprisingly better results of 39.8% with standard craniectomy in severe injury patients. Grindlinger et al. reported a decent 71% good to moderate outcome with impressive 6% mortality rate. In our initial cases we did not replace the bone flaps in spite of satisfactory relaxation of brain in some of our cases. However, later we replaced bone flaps regularly when satisfactory lax brain was achieved following cisternostomy. Inability to replace the bone flap indicates very severe primary injury and cerebral oedema. Though there is no statistical significance between the two groups, the BC group has certainly shown an edge over the other.
Very few studies have compared Cisternostomy with DC and the only retrospective study that has analysed with ICP monitoring is from University of Lausanne with promising results on the utility of cisternostomy in TBI. Iype et al. have claimed good results with cisternostomy in comparison to standard Decompressive Craniectomy in TBI. Giammetti et al. in a recent publication recommended Cisternostomy as safe and adjuvant to Decompressive Craniectomy that showed better results, better control of ICP, lesser ICU (Intensive Care Unit) stay. In our study though we have not compared our cases of Cisternostomy with DC, a favourable outcome of more than 70% in severe TBI certainly opens a positive approach towards the utility of Cisternostomy in TBI. Shorter the pre ventilatory time and shorter duration between injury and surgery time showed better outcome in our series. Literature also has shown reduced ICU admission and shorter hospital stay in patients who underwent Cistrenostomy. Noteworthy complication in our series is the development of hydrocephalus in 5 patients (12.5%) which looks significant and may need to be analysed. Overall two patients died in our series. Cranioplasty was done in those patients who needed the bone flaps to be replaced in the subsequent period.
Limitations of our study are that it is a retrospective study and ICP monitoring was not done.
Basal Cisternostomy is an effective microsurgical procedure in the management of Traumatic Brain Injury. It drains and let out the CSF effectively and relaxes the brain satisfactorily. Our retrospective single-center study has shown more than 70% favourable (Good) outcome with Cisternostomy in severe traumatic brain injury patients. It certainly facilitates replacement of bone flap in most of the patients thus obviating the need for routine Decompressive Craniectomy alone. The incidence of Decompressive Craniectomies is expected to drop significantly in near future when more and more centers start adopting basal cisternostomy as a routine microsurgical procedure in TBI.
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Conflicts of interest
There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]