Letter to the Editor: Multiple Brain Abscesses in Hemophilus parainfluenzae Endocarditis: A Case Report

To the Editor:

A 35-year-old previously healthy male presented with fever, diarrhea, emesis, drowsiness, and left-sided deficit. Examination was remarkable for somnolence and left-sided motor deficit. Brain magnetic resonance imaging (MRI) showed ring-enhancing lesions at the right thalamus, the right pons, and left peduncle with marked restriction diffusion consistent with abscesses (Fig. 1A–1C). Culture of cerebrospinal fluid (CSF) was negative. Surgical intervention was discarded. Empiric antibiotic therapy was started with cefotaxime-gentamicin. Transesophageal echocardiogram showed two vegetations on the mitral valve, abscess, and perforation. Blood cultures showed slow-growing gram-negative bacilli and on day seven, amoxicillin-sensitive Hemophilus parainfluenzae (HP) was identified. The infective endocarditis (IE) required emergent mitral valve surgery.

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FIG. 1.

Magnetic resonance imaging (MRI): multiplanar reformat (MPR) image from contrast-enhanced three-dimensional T1 (CE-3DT1) acquisition, in the axial plane, at the level of the thalamus shows brain abscess, presenting as rim-enhancing rounded lesions. The right medial thalamus (A, arrow), the anterior right pons (B, arrow), and subtle enhancement at the left anterior midbrain (C, arrow), consistent with abscesses. Follow-up MRI (MPR image from CE-3DT1 acquisition), at one month after starting antibiotic therapy, shows a gradual decrease in abscesses (thalamic abscess: D, arrow; pons abscess: E, arrow; midbrain abscess: F, arrow). Susceptibility magnetic resonance sequence shows the susceptibility sign at the level of the abscesses on T2* (G, H, I).

The course of illness was characterized by the regression of the left deficit (5/5 to 3/5) and a gradual decrease in abscesses size until their almost complete resolution at three months (Fig. 1D–1If). Among HACEK-IE, Hemophilus spp. IE are the most frequent. In our cohort of 424 patietns with IE, two (0.4%) were HP-IE. Typically, HP-IE presentation includes large vegetations, native mitral valve involvement, and embolic phenomena, leading to a severe disease. The HP-IEs are subacute in progress and are not associated with cardiac failure. Only half of the patients need valve surgery. ¹ In contrast to the above considerations, our case shows that IE can develop rapidly and can be complicated by cardiac failure even in a young patient without comorbidities.

The diagnosis of HP-IE remains a challenge because of the slow growing characteristics of the organism. In our cohort of 424 patients with IE, two (0.4%) were HP-IE, and one presented with brain abscess (BA) (0.2%). To note, Darras-Jolly et al. ¹ in a study of 26 HP-IE did not report BAs. The thalamus and the brainstem are unusual locations for BAs: 1.8% to 3%^2,3 and 3%, respectively. ² Thalamic abscesses may be revealed by hemiparesis, present in 44%. Subcortical aphasia has only been reported in a few cases. ⁴ Common symptoms of brainstem abscess are unilateral face or extremity numbness or weakness (55%), headache (50%), diplopia (38%), vomiting (38%), and ataxia (30%). Our patient had isolated hemiparesis, most likely related to the thalamic abscess. The brainstem abscesses were small in size, which would explain the absence of brainstem syndromes.

Hemophilus spp. represent 2% of 7,340 of 9,699 BAs with positive cultures in the review by Brouwer et al. ³ Hemophilus parainfluenzae is not listed in the series by Nathoo et al. ² To the best of our knowledge, only one prior case of HP thalamic BA has been reported in a non-IE patient. ⁵

In IE, the differential diagnosis between BA and acute ischemia may be difficult. Contrast enhancement, not observed at the acute phase of the ischemia, strongly indicated a BA. The susceptibility ring, related to hemorrhage in the abscess wall, helps in differentiating BAs from necrotic malignant tumors; it is not observed in brain infarcts. Combined with apparent diffusion coefficient (ADC), it can help to differentiate BAs.

Our case highlights the effectiveness of antibiotic treatment alone, in a patient with HP-IE with multiple and small abscesses (≤2.5 cm). The duration of the treatment varies from six to eight weeks or more, and depends on the resolution of the lesions on the follow-up imaging.