The Unspoken Danger of the Mount Fuji Sign Leading to Sudden Death

Abstract

Traumatic pneumocephalus is not an unusual entity. Mostly, such cases are managed according to the patient’s neurological status, guided by computed tomography (CT) imaging, and the patient responds well to conservative treatment. However, it seldom progresses to tension pneumocephalus, and if it does along with deterioration of the neurological condition, then neurosurgical intervention becomes necessary. On CT, its appearance is named “Mount Fuji” sign. The most widely documented peril involves increased intracranial pressure causing mass effect and, in some cases, cerebral herniation. However, one unspoken aspect leading to sudden death is seizure. We report the case of a 52-year-old male, admitted after vehicular accident responding well to the conservative treatment along with resolution of tension pneumocephalus. However, he developed generalized tonic-clonic seizures leading to sudden death. Through this case report, we will be discussing the association of pneumocephalus with seizures and seizures leading to sudden death.

Introduction

Pneumocephalus is described as pathological accumulation of air in the cranial cavity which predominantly occurs within dural spaces and intraparenchymal and, rarely, in intraventricular cavities. It is typically associated with craniofacial trauma, cranial surgical interventions, fractures of the base of the skull or sinuses, otorhinolaryngeal procedures, epidural or spinal injections, and infections of the brain or middle ear, including otitis media, meningitis, encephalitis, brain abscess involving gas-forming pathogens, and invasion by nasopharyngeal tumors, leading to erosion of skull base.[1]

In majority of cases, management is conservative treatment based on neurological condition and clinical observation guided by radiological imaging, and they respond well. However, if pneumocephalus proceeds to tension pneumocephalus accompanied by deterioration of neurological condition, it requires prompt neurosurgical intervention, involving decompression of trapped intracranial air. Radiological presentation of tension pneumocephalus involves compression of frontal lobes along with enlargement of inter-hemispheric gap. This is known as “Mount Fuji” sign because of its resemblance to a famous Japanese mountain peak. This sign was first proposed by Ishiwata et al. in the year 1988.[2] It is characterized by persistent accumulation of air in the intracranial cavity due to a specific “ball valve” mechanism, subsequently leading to mass effect on brain parenchyma, which is a potentially life-threatening condition.[1] Clinical manifestations include headache, changes in vision, altered mental status, deterioration of Glasgow Coma Score (GCS), seizures, and even death.

Case Report

A 52-year-old man was admitted to our hospital after vehicular accident which occurred about 2 hours ago. During initial evaluation, there were abrasions over the left forearm, hand, and knee. There were no injuries over the head and face and no visible external craniofacial deformity or fractures. He was conscious but disoriented. Bleeding from the ears was present. His initial GCS was E3V4M5. Bilateral pupils were of normal size and normally reacting to light. Investigations were done and chest X-ray showed fracture of the left 3^rd–6^th ribs. USG chest was suggestive of mild left-sided pleural effusion with maximum separation of 12 mm. He was a known case of hypertension and diabetes mellitus. He had normal responsiveness with normal ABG and oxygen saturation.

On noncontrast computed tomography (NCCT) head, there was a longitudinal fracture of the petrous part of the left temporal bone extending up to the middle ear with soft-tissue opacification present in mastoid air cells and middle ear – suggestive of hemosinus with hemotympanum. Another fracture was present involving the squamous part of the left temporal bone, extending into the base of the middle cranial fossa on the left side and sphenoid sinus and transversing it to end at the base of the middle cranial fossa on the right side [Figure 1a]. Hyperdense contents were seen in the sphenoid sinus –suggestive of hemosinus. There was associated extensive pneumocephalus, causing mass effect over bilateral anterior frontal lobes and anterior temporal lobes, seen in the form of mild flattening of the external contour of the above-mentioned cerebral convexities, the Mount Fuji sign in the bilateral anterior frontal region, depicting tension pneumocephalus [Figure 1b]. Multiple air foci/bubbles were also present along the falx, tentorium cerebelli, bilateral cerebral cortical sulci, and basal cisterns. Mild subarachnoid hemorrhage was present in the right temporal region. Ill-defined hypodense areas approaching fluid attenuation (10 Hounsfield units) were present, involving bilateral cerebellar hemispheres (left >right) – possibility of cystic encephalomalacia, likely due to some prior insult. The brainstem was in the midline and revealed normal attenuation. The rest of the brain parenchyma was normal in morphology and attenuation with preserved gray-white matter differentiation.

Figure 1.

(a) Fractures of the base of the skull (Arrows indicate fracture points), (b) Flattening of the external contour of cerebral convexities, the Mount Fuji sign, in the bilateral anterior frontal region

During the hospital stay, the patient was conscious but irritable and was accepting orally. Vitals were stable. Initially, he was managed with oxygen therapy, kept in supine position, prophylactic antibiotic therapy, analgesia, and anti-epileptics. Frequent neurologic checks and repeated computed tomography (CT) scans were done. The second CT scan, performed on day 3, showed an increased volume of the pneumocephalus from 35 ml to 62 ml. However, neurological condition and vitals were stable. The third CT scan, performed on day 5, showed resolution of tension pneumocephalus, with a decrease in volume of air from 62 ml to 30 ml [Figure 2a–c]. The patient was conscious but irritable, and neurological condition along with vitals was stable. However, on day 6, he had generalized tonic-clonic seizures (GTCS), leading to hypoxia. He was immediately intubated and kept on ventilatory support. He also developed hypotension, for which inotropes were started. However, he had sudden cardiac arrest, and despite all resuscitative measures, he could not be revived back and was declared dead.

Figure 2.

(a-c) Change in volume of air in consecutive noncontrast computed tomography of the head. AP: Anteroposterior dimension; CC: Cranial caudal dimension; NCCT: Noncontrast computed tomography

During autopsy examination, there were no external injuries over the head and face. Brownish-black scabbed abrasions were present over the left forearm, hand, and knee joint. Fracture of the 3^rd–6^th ribs was present along the midclavicular line over the left side of the chest. Rest, all organs were unremarkable. There was no subgaleal hemorrhage. On opening the skull and further exploration, there was longitudinal fracture of the petrous part of the temporal bone on the left side. Another linear fracture of the squamous part of the temporal bone was present, extending over the middle cranial fossa of the base of the skull on the left side and the greater wing and body of the sphenoid bone till the middle cranial fossa on the right side as well. Flattening of both external contours of the cerebral convexities was present, involving both anterior frontal lobes and left temporal lobe depicting the autopsy findings of Mount Fuji sign as seen in available antemortem CT findings. A thin layer of seroma was confined over the surface convexity of the left parietotemporal region [Figure 3a]. Minimal subarachnoid hemorrhage was present over the cerebellum [Figure 3b]. Contusion was present over the right temporal region [Figure 3c]. The cause of death in this case was given craniocerebral damage and its complications, due to blunt trauma/surface impact over the head.

Figure 3.

(a) Flattening of external contours of the cerebral convexities involving both anterior frontal and left temporal lobes, with a thin layer of seroma over the left parietotemporal region, (b) Subarachnoid hemorrhage over the cerebellum, (c) Contusion over the right temporal lobe

Discussion

Efforts to optimally treat neurotrauma cases often encounter a variety of challenges. Early detection of the underlying cause greatly facilitates appropriate care and treatment planning of the patient. Initial clinical evaluation is important, including GCS, symptoms of headache, nausea, vomiting, reduced vision, and changes in pupillary reaction and neurological deficits. Head CT scan constitutes an important investigation. GCS is one of the tools for monitoring posttraumatic head injury patients. When there are fractures of the base of the skull and sinuses, coughing, straining, and sneezing cause the sinuses to generate a high pressure, forcing air into subdural space, and in certain case, into the brain to reach the ventricles.[3] Air can become trapped in the brain via a check valve mechanism caused by bony fragments, foreign bodies, dural flaps, sinus mucosa, or granulation tissue leading to tension pneumocephalus. Majority of pneumocephalus cases resolve on their own by conservative measures.

The CT findings should be correlated with deterioration of neurological condition of the patient. Tension pneumocephalus can lead to increased intracranial pressure, resulting in deterioration in neurological condition, altered level of consciousness, seizures, cerebral herniation, and even death, if untreated. Prompt decompression is the treatment of choice, and it can be done through burr hole, needle aspiration, craniotomy, or ventriculostomy, along with identifying and sealing the dural defect. In this case, the early onset of tension, pneumocephalus was evident on the NCCT head, and the patient was conscious, and there were no neurological deficits, but he was irritable. Accordingly, the patient was managed conservatively and was kept under observation. The second scan showed increased tension pneumocephalus, but again, there was no neurological deficit, and vitals were also stable. In the third scan, there was resolution of the tension pneumocephalus, and he was responding well to the conservative treatment and was slowly taking oral feeds, but on the 6^th posttrauma day, he developed GTCS leading to hypoxia, after which he developed hypotension followed by cardiac arrest and, finally, succumbing to the same.

Increased intracranial pressure leading to mass effect and cerebral herniation is one of the widely documented dangers of tension pneumocephalus. However, another danger of the Mount Fuji sign resulting in sudden death is seizure. In one of the studies, it has been reported that widespread pneumocephalus can lead to status epilepticus.[4] It has been observed in the literature that even when there was no direct handling of brain parenchyma, the intracranial finding was suggestive of pneumocephalus, and there was an association of pneumocephalus leading to seizures. This can further lead to the death of the person. There was a reported case of epidural lumbar puncture leading to pneumocephalus and further to seizures.[5] Pneumocephalus leading to nonconvulsive status epilepticus was observed following suprasellar arachnoid fenestration of cyst done with endonasal transsphenoidal procedure.[6] GTCS were also noted after the development of frontal lobe pneumocephalus in a patient after decompression lumbar surgery for severe lumbar stenosis.[7] Apart from trauma and neuro- and spinal surgeries, pneumocephalus was also noted in one case of the otological procedure following cochlear implantation which further led to seizures.[8]

GTCS are most frequently observed in head injury patients. They emerge within the cerebral parenchyma, if there is any kind of insult or injury or rapid involvement of both cortical and subcortical areas of the brain.[9] Regarding the pathogenesis of pneumocephalus leading to seizure, there is cerebral contour flattening of frontal lobes, which leads to further mechanical stretching of the parenchyma of the cerebral surface and its vasculature, leading to changes in regional circulation followed by functional failure of neurons which could have led to the development of seizures. Furthermore, the disruption of metabolism and circulation caused due to extended epileptic activity can subsequently lead to cytotoxic edema in the epileptic cortical neurons.[6]

Sudden death due to seizures can happen during or right after GTCS, as a result of arrhythmias and postictal apnea that can lead to asystole and eventually death. Many theories have been put forth to explain sudden unexpected death in GTCS, including subsequent fatal cardiac arrhythmia which can be precipitated by discharge from seizure operating through the autonomic nervous system resulting in autonomic dysregulation followed by drastic alterations in cardiopulmonary activity which results in hypoxia leading to cardiac dysfunction and subsequent death.[10] In one of the studies, it was seen that respiratory depression, which was driven by seizures, was a more prominent cause of sudden death, instead of cardiac arrhythmias as the immediate cause.[11] Furthermore, GTCS linked with persistent fatal arrhythmias could make the healthcare management of such kind of patients more difficult.

Conclusion

A meticulous postmortem examination, combined with the knowledge of existence of such a rare entity, can go a long way in arriving at a definite cause of death, thereby giving closure and helping the bereaved families in medico-legal cases and also helping in improving the standard of patient care and devising treatment plan of such patients in the hospital.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.