Intracranial Abscess Mimicking Stroke in Pregnancy

Luissa Kiprono, DO, Keesler AFB, Miss, David McKenna, MD, Wright State University, Boonshoft School of Medicine, Hugh Moncrief, MD, Miami Valley Hospital, and Gary Ventolini, MD, Wright State University, Boonshoft School of Medicine, all in Dayton, Ohio

Published Online: August 2, 2007 - 1:32:30 PM (CDT)

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Pregnant women and their fetuses are susceptible to a broad spectrum of infectious diseases. Some infections, mainly because of decreased immune surveillance during pregnancy, may be serious and even life-threatening, and others may have a profound impact on neonatal outcome.¹ Brain abscess is a potentially life-threatening complication that is only rarely associated with pregnancy. The Streptococcus milleri group organisms are part of the indigenous oral flora and are regarded as the causative organisms of suppurative infections, such as multiorgan abscesses. We describe an unusual case of a pregnant woman with a respiratory infection that involved an atypical onset and symptoms resembling an acute intracranial anoxic episode.

Case Presentation

A 36-year-old white woman (gravida 3, para 2) was examined at 28 weeks gestation in the emergency department because of productive yellowish cough associated with upper back discomfort, as well as chest congestion, chills, and fatigue. She denied any obstetric symptoms and her pregnancy was otherwise uncomplicated. Her history was remarkable only for gastroesophageal reflux disease. Physical examination revealed the patient was afebrile and tachycardic, had reduced ventilation, basilar rales, and wheezing. Laboratory data demonstrated leukocytosis of 22,000/mm³ (22 x 10⁹/L), with a left shift. Arterial blood gas values were normal. The urinalysis was positive for large ketones, leukocyte esterase, bacteria, and white blood cells. A chest x-ray showed a patchy infiltrate in the left lower lobe. The patient was diagnosed with bacterial pneumonia and dehydration and was admitted to the hospital. She received intravenous (IV) azithromycin (Zithromax) 500 mg/day and IV cefuroxime sodium (Zinacef) 1.5 g every 8 hours. The obstetric ultrasound was normal, and the patient was discharged on the third day, with a prescription for oral antibiotics for the next 14 days.

Three days later, the patient returned to the emergency department, with complaints of severe headache, decreased alertness, paresthesias to the left side of her face, left-arm numbness and clumsiness, and reduced range of motion of the left lower extremity. A right-sided cerebrovascular accident was diagnosed; magnetic resonance imaging (MRI) revealed 3 intracranial lesions. Brain abscess was suspected, and the patient was readmitted.

Medical therapy was initiated with metronidazole (Flagyl IV) 500 mg IV every 8 hours and ceftazidime (eg, Ceptaz, Fortaz, Tazicef) 2 g IV every 8 hours. Adjunctive medication included dexamethasone to decrease cerebral edema. The fetus exhibited normal biometry, reassuring biophysical profile, and 2 reactive nonstress tests. On the second day, the patient developed a grand-mal seizure and was treated with IV phenytoin to prevent recurrent seizures.

Her headache worsened, and the patient became comatose. A second MRI showed 4 lesions—in the right temporal lobe, right occipital lobe, above the body of the right lateral ventricle, and within the right parietal region (Figure 1), consistent with cerebral abscesses, with a ring-enhancing pattern in the right cerebrum. The midline structures shifted to the left (Figure 2), with a mass effect at the midbrain and the ventricular level, and partial uncal herniation. Emergent craniotomy and drainage of the abscesses was performed. Third cranial-nerve palsy was noticed before intubation. Cultures were positive for S milleri group organisms.

Figure 1?MRI of the brain showing lesions in the lateral ventricle (red arrow), right parietal (yellow arrow), and right occipital lobe (blue arrow).

Figure 2?MRI of the brain showing the midline shift to the left (red arrow), with a mass effect at the midbrain and the ventricular level.

After surgery, the patient recovered rapidly and was discharged 7 days later, in good condition but with residual left-sided motor deficits. The patient continued to take dexamethasone and phenytoin for the remainder of the pregnancy, and IV antibiotics were continued for 1 month. Labor was induced at 39 weeks, and the delivery was uneventful. The 3459-g infant was healthy, with 1- and 5-minute Apgar scores of 9 and 9, respectively. The mother was discharged on postpartum day 2 in a stable condition. A 6-month follow-up brain MRI showed no evidence of abscess, intracranial edema, or residual deficits. No neonatal complications occurred, and the infant was developmentally on track at periodic pediatric evaluations.

Discussion

A variety of pyogenic organisms give rise to brain abscesses. These lesions are characterized by progressive stages of purulent exudate formation and encapsulation. S milleri group organisms are part of the indigenous oral flora. Because of the great variability of single characteristics within this group, it has not been possible to demarcate further subgroups. Streptococci that belong to the S milleri group are slow-growing, catalase-negative, gram-positive cocci, usually forming "minute" colonies on blood-agar. Most of the strains are aerobic, some grow better in a carbon dioxide?stimulated environment, and still others are strict anaerobes.

The normal habitat of S milleri group has not been firmly established. The bacteria have been isolated from the nasopharynx, external ear, and vagina. S milleri group is the causative organism of many suppurative infections, including oral, brain, and lung abscess, as well as empyema, with and without bacteremia. Intracranial abscesses are probably the most pathognomonic.² In one study of 46 cases of brain abscess, S milleri group organisms were most frequently isolated in 43% of the cases.³

A brain abscess may originate as a result of:

• Penetrating injury to the skull (eg, trauma, surgery)
• Contiguous spread of infection from an adjacent focus (eg, chronic otitis media, sinusitis, dental infections)
• Metastatic spread from a distant infection (eg, pulmonary infection, endocarditis), although the inability to locate a primary source of infection is common.⁴

The first manifestation of a brain abscess may be the signs and symptoms of acute infection, such as chills or fever, as was the case in our patient, and/or signs of insidious meningeal irritation. Because edema develops rapidly in the adjacent brain tissue, headache, vomiting, and convulsions are early signs.

Manifestations of brain abscess that resemble a stroke are uncommon.^5,6 The development of focal neurologic deficits resembling those of an acute vascular insult that was seen in our patient represents an atypical presentation that is inconsistent with the classic symptoms usually seen with a brain abscess—lethargy with fever and chills, anemia, and cachexia.

Definitive treatment for a brain abscess is surgical, with drainage of the abscess cavity using needle aspiration or by total excision of the abscess, including its capsule. In our patient, the latter could not have been considered because of the vital structures at the site of the lesions involved and the risk of long-term neurologic sequelae. Any surgical specimen should be cultured to identify the infective organism(s) and guide the selection of an appropriate antibiotic regimen.⁷

High-dose parenteral antibiotics should be administered empirically preoperatively, and should be continued for 2 to 4 weeks postsurgery. The antibiotic regimen should include chloramphenicol (Chloromycetin Sodium Succinate) or metronidazole, both of which are active against all obligate anaerobes.⁸ Although the definitive treatment of brain abscesses is surgical, it has been suggested that selected patients who are not in imminent danger from increased intracranial pressure may qualify for a trial of nonoperative therapy.⁴

Our patient was started on parenteral therapy first, because of her pregnant status, and because her abscesses were in early cerebritis stage (ie, thick-core absent), when antibiotics could still penetrate into the abscess. Surgery was performed without delay once the symptoms worsened despite medical therapy.

A MEDLINE search of the English-language literature revealed only 12 cases of brain abscesses complicating pregnancy that were published in the past 20 years.⁹ Of these, only 1 case described a brain abscess associated with a sudden, strokelike onset.⁶ To our knowledge, ours is the second case with this condition and is the first case of S milleri group"-"induced brain abscess mimicking stroke in pregnancy reported to date.

Conclusion

The rapid onset of neurologic symptoms in our patient was uncommon and was suggestive of a cerebrovascular lesion. Imaging studies were instrumental for arriving at the correct diagnosis. During pregnancy, any medical condition, but infections in particular, should be fully investigated and promptly and aggressively treated, to avoid rapid deterioration of maternal status and potentially severe damage to the fetus, or even pregnancy termination. S milleri group organisms play an important causative role in respiratory infections and may evolve into life-threatening complications during pregnancy.

References

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