Extradural Hemorrhage Secondary to Skull Pin Fixation Manifesting as Intractable Intraoperative Brain Swelling
Provision of a relaxed brain is one of the essential requirements of successful anesthetic management during neurosurgical procedures which allows adequate surgical access, retraction, and dissection. Failure to achieve proper brain laxity may cause brain herniation through craniotomy or excessive retractor pressures causing retractor ischemia. We experienced a rare scenario where a patient developed unexplained tense brain intraoperatively which could not be corrected by conventional rescue measures. Postprocedural imaging revealed the presence of an extradural hemmorhage (EDH) secondary to pin insertion as the cause of the tense brain.
A 25-year-old male patient was posted for suboccipital craniectomy and tumor excision for cerebellar glioma. After induction of general anesthesia, he was turned prone and the head was fixed over a 4-pin Sugita’s frame. Before craniectomy, mannitol (0.5 mg/kg) was administered, and after opening the dura a perfectly relaxed cerebellum was observed. Thirty minutes later when about half the tumor had been removed, the surgeons noticed a gradually increasing tenseness of the cerebellum. Immediate search for cause ensued. Airway obstruction and kinked neck veins were excluded. Anesthetic depth and analgesia were intensified, and the head was slightly elevated. A marginal improvement was noticed, but within 10 minutes the cerebellum again started to swell. Hyperventilation was instituted to bring down PaCO2 to 30 mm Hg (baseline PaCO2, 33 mm Hg), but the brain swelling continued to increase. Extra doses of mannitol also failed to provide any benefit. The cerebellum by now had become severely tense obscuring the surgical field. The surgeon was forced to temporarily terminate the procedure and perform a lax duroplasty and closure. The paralysed and ventilated patient was then shifted urgently to the radiology suite for a computed tomographic (CT) scan. CT scan revealed the presence of an EDH adjacent to the area where the inferior right-sided pin had been screwed against the skull (Fig. 1). The patient was then again shifted back to the operation theater where he underwent an emergency decompressive craniotomy and evacuation of the EDH.
Intraoperative tense cerebellum during prone positional neurosurgeries may develop secondary to surgical, anesthetic or positional reasons. Uncommon causes like urinary retention have also been implicated.1 This necessitates expeditious reduction of brain volume by treating the specific cause of tense brain. Development of EDH following pin insertion is a known complication.2 In our case, the adjacent locations of the EDH and the pin sites, made pin insertion a prime suspect in the development of EDH. Intraoperative EDH might also develop due to coagulopathy,3 but in our case the coagulation parameters were found to be normal. Acute decompression of supratentorial compartment due to cerebrospinal fluid drainage or tumor excision can cause stripping of the dural veins and EDH formation.4 Although no breach of the inner cortex or fracture line on the exposed bone was observed, we postulate that some amount of bleeding might have initiated during pin tightening from the marrow or inner cortex of skull. Partial tumor excision leads to precipitous loss of intracranial pressure thereby causing loss of the tamponading effect and aggravating the bleed. The additional epidural space created and negative pressure following brain displacement consequent to tumor resection allowed blood to accumulate. As the bleeding was diametrically opposite to the surgical field, it could not be appreciated and the gradually increasing hemmorhage caused cerebellar swelling. The added bolus of mannitol might have proved counterproductive as brain shrinkage caused further loss of intracranial pressure and increased the bleeding.