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Doctors Find Air Pocket Hidden in Man's Brain

March 19, 2018

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Pneumocephalus and comminuted fracture of the frontal sinus
Photo credit: CT scan by James Heilman, MD - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=49086936

Doctors treating a patient who had complained of repeatedly losing his balance made an unexpected discovery: The 84-year-old man had a 3.5 inch pocket of air in his brain. A CT scan of the man's head revealed a large air cavity compressing his right frontal 1) ___. The condition is known as pneumocephalus (PNC). Treatment for PNC depends on may factors, including symptoms. Condition commonly compresses the frontal lobe, can affect voluntary muscle movement. The man had been referred to the emergency room by his primary physician in Northern Ireland. He told his doctor about weeks of recurrent falls and three days of left-side arm and leg weakness, according to the report, published in the journal BMJ Case Reports, March 2018. The patient did not have any visual or speech impairments and did not seem confused or have facial weakness, according to the authors. The physicians performed scans of the brain to identify any signs of bleeding or brain damage caused by blocked blood vessels, but what they found was much more unusual, a small benign tumor. A computed tomography scan of the patient's 2) ___ showed a large pocket of air -- also called a pneumatocele -- in the patient's right frontal lobe. When pneumatoceles are present in the brain, the condition is often referred to as PNC. They most commonly compress the frontal lobe, which plays a large role in voluntary muscle movement. The air pocket was right behind the frontal sinus and above the cribriform plate, which separates the nasal cavity from the cranial cavity. This was a rare presentation with a lot of 3) ___ in his brain. An MRI of the man's brain also showed a small benign bone tumor, or osteoma, that had formed in the man's paranasal sinuses and was eroding through the base of the skull, causing air to leak into the cranial cavity. Sometimes, there can be a one-way valve, and air comes in and can't get 4) ___. The pressure from the air cavity may have also caused a small stroke in the patient's frontal lobe, resulting in the left-side weakness and gait instability that prompted his hospital visit.

According to a 2015 study in the journal Surgical Neurology International, trauma is responsible for approximately 75% of pneumocephalus cases. The remaining cases are often complications of neurosurgery; ear, nose, and throat surgery; sinus infections; or, as in this case, bone tumors. Treatment for pneumocephalus depends on several factors, particularly the symptoms involved. Many cases of pneumocephalus have no symptoms and eventually become absorbed by the body without treatment. In more serious cases, such as those that cause high 5) ___ pressure in the brain or impaired consciousness, decompression surgery to alleviate pressure on the brain may be required. In this case, the patient was offered surgical treatment from a team of neurosurgeons and ENT surgeons. The procedure would have involved temporary surgical removal of part of the frontal bone of the skull and excision of the bone tumor to close the leak that was sending air into the brain. However, due to his age and other health factors, the patient declined surgery and instead chose conservative treatment involving medication to prevent a secondary 6)___. When the patient returned for a 12-week follow up visit, he felt better and no longer complained of left-side muscle weakness.

Background: Pneumocephalus (PNC) is the presence of air in the intracranial cavity. The most frequent cause is trauma, but there are many other etiological factors, such as surgical procedures. PNC with compression of frontal lobes and the widening of the interhemispheric space between the tips of the frontal lobes is a characteristic radiological finding of the "Mount Fuji sign."

Case Description: A 74-year-old male was diagnosed with meningioma of olfactory groove. After no improvement, surgery of the left frontal craniotomy keyhole type was conducted. A CT (computed 7) ___tomography) scan of the skull performed 24 hours later showed a neuroimaging that it is described as the silhouette of Mount Fuji. The treatment was conservative and used continuous oxygen for 5 days. Control CT scan demonstrated reduction of the intracranial air with normal brain parenchyma.

Conclusion: In a review of the literature, there was no finding of any cases of tension PNC documented previously through a supraorbital keyhole approach. There are a few cases reported of patients with Mount Fuji signs that do not require surgical procedures. The conservative treatment in our report leads to clinical and radiological improvement as well as a reduction in hospitalization time.

PNC and TP: The terms pneumocephalus (PNC) and tension pneumocephalus (TP) were created by research scientists, Wolff and Ectors, respectively, even though TP has been described in the early literature. PNC is the presence of air within the intracranial cavity. When this circumstance causes increased intracranial pressure that leads to neurological deterioration, it is known as TP. Ishiwata et al. described the image produced by PNC in subdural collections that separated both frontal lobes as similar in appearance to the silhouette of the famous Fuji Volcano in 8) ___. CT is a golden standard for PNC or TP diagnostics and it only requires 0.55 mL of air to be detected, whereas a simple skull radiograph requires at least 2 mL. Air between the frontal tips is a characteristic finding of the "Mount Fuji sign," which means there is the greater pressure of air than the surface tension of cerebral fluid between the frontal lobes. In anterior cranial fossa, the dura mater is thin and closely applied to bone and the arachnoids adherent to frontal lobes; therefore, the air is trapped in the subdural space of the anterior cranial fossa. When there is a bilateral compression of the frontal lobes without separation of the frontal tips, it is called “peaking sign,“ which was previously linked to TP. An MRI axial view of fluid-attenuated inversion recovery revealed the Mount Fuji sign with collapsed frontal lobes and widening of the interhemispheric space between the bilateral tips of the frontal lobes. The Mount Fuji sign indicates more severe PNC than the peaking sign and the necessity of emergent decompression, although in some cases, a patient with Mount Fuji sign sometimes does not need a surgical procedure.

PNC usually gets absorbed without any clinical manifestations. The conservative treatment involves placing the patient in the Fowler position of 30o, avoiding Valsalva maneuver (coughing and sneezing), administering pain and antipyretic medications to prevent hyperthermia, and osmotic diuretics. With these measures, reabsorption was observed in 85% of cases after 2-3 weeks. In other cases, different procedures have been used, like hyperbaric oxygenation (HBO2) therapy sessions, where normobaric oxygenation is administered continuously at 5 L/min for 5 days, resulting in the reabsorption of nitrogen into the blood stream and a reduction in the volume of the intracranial air. In a clinical trial, clinical improvement was seen in all patients; however, the treated group experienced a lower rate of meningitis compared to the control group, and the length of the hospital stay was significantly higher in the control group compared to the treated group. The use of an oxygen mask increases the reabsorption of PNC compared to a nasal catheter. When clinical signs appear, such as intracranial hypertension or impaired consciousness that endangers the life of the patient, treatment consists of emergent decompression to alleviate pressure on the brain parenchyma. Also, air is toxic to neurons, causing further damage to the already compromised parenchyma, and that leads to cerebral edema surrounding the air that evolves into encephalomalacia. Treatment options for TP include the drilling of burr holes, needle aspiration, and closure of the dural defect. If the frontal sinus is open during surgery, it is aggressively managed with exenteration of the mucosa, sinus packing with abdominal fat or a piece of temporal muscle and covered with frontal fascia. There are a few cases reported of asymptomatic massive PNC or patients with Mount Fuji signs that do not require surgical procedures. Traveling by plane is considered high 9) ___ because as the height increases, atmospheric pressure decreases, and the gasses expand. Therefore, a pneumothorax could become hypertensive, a bulla could expand or break, and PNC could enlarge and produce more intracranial hypertension. However, it has been observed that military patients with posttraumatic and/or post craniotomy PNC, who underwent long-range air evacuation from a combat theater in military aircraft, did not sustain a temporary or permanent neurologic decline as a result of air transportation. Therefore, PNC in patients with head injuries and craniotomies was not likely by itself to be an absolute contraindication to air evacuation. Finally, the medical guideline recommends waiting at least 7 days to fly after a transcranial or spinal surgery that could introduce gas into the skull.

TP must be treated by surgical revision when it causes intracranial hypertension and/or deterioration of consciousness. There are a few cases reported of patients with Mount Fuji signs that do not require surgical procedures. The conservative treatment in these patients is with HBO2 therapy sessions in a monoplace hyperbaric chamber with 100% 10) ___ concentration or normobaric oxygenation administered continuously at 5 L/min at least for 5 days. This treatment should lead to clinical and radiological improvement as well as a reduction in hospitalization time.

Sources: Medline.com; nih.gov; Wikipedia; PubMed.gov; Mark Lieber CNN Health.com; Copyright: © 2015 Surgical Neurology International This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.How to cite this URL: Dabdoub CB, Salas G, N. Silveira Ed, Dabdoub CF. Review of the management of pneumocephalus. Surg Neurol Int 29-Sep-2015;6:155. Available from: http://surgicalneurologyint.com/surgicalint-articles/review-of-the-management-of-pneumocephalus/

ANSWERS: 1) lobe; 2) brain; 3) air; 4) out; 5) blood; 6) stroke; 7) tomography; 8) Japan; 9) risk; 10) oxygen

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