An 81‐year‐old man presented with a 4‐ to 5‐day history of increasing confusion, combativeness, and personality changes. There were no associated fevers or chills. Patient denied photophobia, neck stiffness, headache, trauma, or recent intoxication. On presentation he was afebrile and had no focal neurological signs, nuchal rigidity, otorrhea, or rhinorrhea. His lung exam was clear, his heart exam showed regular rhythm without murmurs, his abdomen was soft and obese with no hepatosplenomegaly. Laboratory studies including electrolytes, liver studies, oxygen saturation, serum glucose, complete blood count, and toxicology screen were normal. Computed tomography of his head revealed a focus of air in the frontal horn of the left lateral ventricle communicating with a porencephalic cyst, and bilateral dehiscence of the tegmen tympani. There was interval appearance of fluid in the left middle ear and left mastoid air cells following a cisternogram, indicating a communication. On further questioning, the patient stated that he had been blowing his nose heavily secondary to a recent upper respiratory infection prior to the appearance of his symptoms.
Altered mental status is a common problem encountered by the hospitalist with a very broad differential diagnosis. Through a systematic workup, most rare causes are easily uncovered. Neurologic causes include trauma, inflammation of the brain including encephalitis, and normal pressure hydrocephalus. Mimickers of altered mental status include a postictal period of a seizure and dysarthria from a stroke. Respiratory causes include hypercapnia and hypoxia. Metabolic causes include intoxications, hepatic encephalopathy, uremia, and disorders in sodium, calcium, and glucose. Endocrine causes are most commonly thyroid disorders and diabetes related. Finally, altered mental status may be secondary to hyperthermia, hypothermia, or overwhelming sepsis. In our patient, air, a cause of inflammation, was seen on head CT. There was no evidence of another etiology for the altered mental status. The tegmen tympani is a thin bone separating the tympanic cavity from the middle cranial fossa, which can be damaged through embryologic defects, bony resorption, or from erosion by cerebrospinal fluid pulsations over this barrier. Pneumocephalus is fairly uncommon, and typically results from trauma, malignancy, infection, or a surgical complication. In this patient, the increased pressure in the tympanic cavity coupled with his anatomic abnormality damaged the dura and introduced air into the patient's intracranial cavity via a “ball‐valve” mechanism.
Given the ubiquity of barotrauma through nose‐blowing, valsalva, and air travel, pneumocephalus remains an important consideration in the altered mental status workup.
To cite this abstract:Cerreta K. Colliding with the Very Air He Breathes. Abstract published at Hospital Medicine 2013, May 16-19, National Harbor, Md. Abstract 246. Journal of Hospital Medicine. 2013; 8 (suppl 2). https://www.shmabstracts.com/abstract/colliding-with-the-very-air-he-breathes/. Accessed April 2, 2020.