A 65-year-old man presented to the ED via EMS with symptoms of stroke. The paramedics stated his right-sided weakness and speech difficulty started 40 minutes prior to presentation in the ED. En route to the hospital, paramedics observed four episodes of facial twitching.
Vitals signs were significant for a rectal temperature of 100.2°F and a fingerstick blood sugar of 220 mg/dL. History of present illness was significant for a diagnosis of left otitis media treated with Augmentin and Vicodin at an urgent care center one day prior to presentation. Past medical history included hypertension, hypercholesterolemia, and diet-controlled borderline diabetes mellitus.
He appeared confused and did not follow commands. He had a right lateral gaze, a right pronator drift, and global aphasia. Left tympanic membrane was perforated with purulent discharge. No mastoid tenderness or overlying skin changes were noted.
A head CT scan without contrast was performed, and revealed an ill-defined low attenuation lesion within the posterior left temporal lobe with associated pneumocephalus. Given ipsilateral opacification of the mastoid air cell and middle ear, findings were concerning for otomastoiditis complicated by intracerebral abscess. A follow-up maxillofacial CT scan with contrast showed thinning of the overlying roof of the temporal bone with dehiscence at multiple locations. A focus of associated pneumocephalus was identified. No definite abnormal parenchymal enhancement was identified, but the findings were consistent with intracerebral abscess complicating otomastoiditis.
Laboratory studies including complete blood count with differential showed WBC 11.54 with 88.2% neutrophils. Pre-operative labs and blood cultures were drawn; the patient was given Levetiracetam, ceftriaxone, and vancomycin, and taken to the operating room by neurosurgery and ENT.
A left ear culture grew Pseudomonas oryzihabitans and Streptococcus pneumoniae. An intracranial abscess grew S. pneumoniae. The patient did well post-operatively, and was discharged home on IV antibiotics.
A brain abscess is a focal, suppurative collection in the brain parenchyma resulting from an infection, trauma, or neurosurgery. Approximately 1,500 to 2,000 cases of brain abscesses are diagnosed in the United States annually, with an estimated one in 10,000 being hospitalized. (Int J Infect Dis 2006;10:103.) Rates are higher in certain high risks groups, including patients with HIV/AIDS. (N Engl J Med 2014;371:447.)
Bacterial invasion is from direct or hematogenous spread. Direct spread makes up 20 to 60 percent of all abscesses, which are caused by otitis media, mastoiditis, dental and other oropharyngeal diseases, or sinusitis, and usually result in a single abscess. (Laryngoscope 1998;108:1635.) Ear infections are decreasing as a cause of brain abscesses in developed countries, but sinus infections continue to be an important consideration. (Laryngoscope 1998;108:1635.) When infection spreads from the mastoids or middle ear to the CNS, the cerebellum, temporal lobes, or both are most often involved. (Laryngoscope 1998;108:1635.) The most frequently isolated pathogen in acute mastoiditis is S. pneumoniae, with a prevalence of approximately 30 percent with minimal variation worldwide. (Laryngoscope 1998;108:1635; QJM 2002;95:501.)
Common symptoms and signs include headache in 70 percent of cases, mental status changes in 65 percent, focal neurological deficits in 65 percent, fever in 50 percent, seizures in 25 to 35 percent, nausea and vomiting in 40 percent, nuchal rigidity in 25 percent, and papilledema in 25 percent. (N Engl J Med 2014;371:447; QJM 2002;95:501.)
The classic triad of fever, headache, and a focal neurological finding is only present in 20 percent of patients. Fever is absent in about 50 percent of patients with brain abscess at the time of the initial presentation. (N Engl J Med 2014;371:447; QJM 2002;95:501.) A lesion in the temporal lobe may lead to an ipsilateral headache, aphasia, and possibly a visual field defect. Hematogenous spread from bacteremia usually leads to multiple abscesses, usually in the territory of the middle cerebral artery. (N Engl J Med 2014;371:447; QJM 2002;95:501.)
As many as 85 organisms have been cultured from blood, CSF, or infection sites of patients with brain abscesses. The most common organisms are Streptococcus spp. and Staphylococcus spp. (N Engl J Med 2014;371:447.) A meta-analysis by Brouwer, et al. found Pseudomonas spp in only two percent of all cultured bacteria. P. oryzihabitans is rare and opportunistic, and is an interesting isolate in our case. It is most commonly associated with catheters, other foreign body causes of bacteremia, and is interesting because this patient had no previous implantation of surgical objects. (Microb Ecol 2011;62:505.)
Case fatality rates from brain abscesses have decreased from 40 to 10 percent, with rates of full recovery increasing from 33 to 70 percent over the past 50 years. These improvements have been attributed to advancement in antibiotics, stereotactic biopsies, and advanced imaging techniques such as MRIs and CT scans. (N Engl J Med 2014;371:447.)