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[Presentation of Case]
The 52-year-old woman, with a history of migraine, had been otherwise well until 1 October, 2013, when fevers and chills developed. She was seen at an outside clinic and was treated as upper respiratory tract infection, without benefit. Disorientation and general malaise developed on 6 Oct, 2013, for which she was sent to another hospital, where a computed tomography of the brain revealed a hypodense lesion in the right frontal lobe, measuring 2.8 X 2.5 X 2.5 cm, with peri-focal edema. She was referred to the outpatient clinic of neurosurgery at this hospital on 8 Oct, 2013. Due to progressive headache, she was admitted to the emergency department at this hospital and the results of the laboratory tests are showed in Table 1. The magnetic resonance imaging of the brain revealed a large lobulated mass in the white matter of the right frontal lobe, measuring 4.8 X 2.8 X 3.5 cm, with significant peri-focal edema (Figure 2). The magnetic resonance spectroscopy at the contrast enhancing margin showed elevation of the lactate/lipid peak, suggesting brain abscess. Treatment with ceftriaxone and metronidazole was begun. She was admitted for surgical intervention on 11 Oct, 2013.
Worsening consciousness was noted after hospitalization and emergent computed tomography of brain showed increase of the size of the brain abscess. Emergent right frontal trephination for abscess drainage was performed on 13 Oct, 2013. She was transferred to the neurosurgery intensive care unit for post-operation care and subsequently to the general ward on 16 Oct, 2013. The echocardiography showed no vegetation of the valves. A dental consultation revealed chronic periodontitis. A culture of an abscess aspirate grew Fusobacterium nucleatum (3+) and Parvimonas micra (3+). Laboratory data on 7 Nov, 2013 showed neutropenia (WBC 2150/μL, Seg 38.5%), for which antibiotics were considered causative. An infection consultation was obtained and ceftriaxone was changed to vancomycin. On examination, continuous bruits were noted on auscultation at the right mid-axillary region, for which a diagnosis of pulmonary arteriovenous malformation was made. The computed tomography of the chest on 26 Nov, 2013 showed right pulmonary arteriovenous malformation and a nodule with ground-glass opacity at the left upper lobe ground. The computed tomography of the brain on 26 Nov, 2013 did not show significant change of the abscess size. Vancomycin was changed to penicillin, followed by a switch to meropenem because of concerns about penicillin allergy. A chest surgeon was consulted for surgical intervention of the pulmonary arteriovenous malformation, which the patient and family declined. On 10 and 13 Dec, 2013, metronidazole and meropenem were discontinued, respectively. She was discharged on 17 Dec, 2013.
On 8 Jan, 2014, a sudden onset of facial asymmetry with shallow right nasolabial fold and drooling developed, followed by aphasia and impaired comprehension. She was admitted to the emergency department at this hospital. The magnetic resonance imaging of the brain revealed infraction involving the left middle cerebral artery territory and right cerebellum. The computed tomography of the chest on 14 Jan, 2014 showed engorged pulmonary feeding arteries and drainage veins at two foci of the right lower lobe (Figure 3). She received trans-arterial embolization for the pulmonary arteriovenous malformation on 23 Jan, 2014. She was discharged on 25 Jan, 2014.
Table 1 Results of the laboratory studies
Hemogram
|
RBC
M/uL |
HB
g/dL |
MCV
f/L |
PLT
K/uL |
WBC
K/uL |
Seg
% |
Band
% |
Lym
% |
Eos
% |
Baso
% |
Mono
% |
2013/10/11 |
4.57 |
14.4 |
91.2 |
202 |
9.86 |
87.7 |
0 |
8.9 |
0.0 |
0.1 |
3.3 |
Biochemistry
|
BUN
(mg/dL) |
Cr
(mg/dL) |
Na
(mmol/L) |
K
(mmol/L) |
ALT
(U/L) |
Glu (mg/dL) |
2013/10/11 |
12.5 |
0.5 |
138 |
4.0 |
8 |
168 |
Figure 1. The chest radiograph showed that increased lung markings at the right lower lung.
Figure 2. The magnetic resonance imaging of the brain revealed a large lobulated mass in the white matter of the right frontal lobe, measuring 4.8 X 2.8 X 3.5 cm, with significant peri-focal edema
Figure 3. The computed tomography of the chest showed engorged pulmonary feeding arteries and drainage veins at two foci of the right lower lobe
[討論]
本病例為肺動靜脈畸形(pulmonary arteriovenous malformation)引起腦膿瘍 (brain abscess)的個案。腦膿瘍為腦實質局部、化膿性的感染，通常有一富含血管的外膜。而沒有外膜的化膿性的腦實質感染，多被稱為腦炎 (cerebritis)。
腦膿瘍的感染途徑可能來自：1. 鄰近組織的感染，例如鼻竇炎(paranasal sinusitis)、中耳炎、乳突炎(mastoiditis)或牙周感染(periodontal infection)，約佔腦膿瘍案例的三分之一，其中源自中耳的感染好發於顳葉(temporal lobe)與小腦；2. 經血液感染的腦膿瘍，約佔25%，多發生於中大腦動脈灰質白質交界處，血源性感染的來源有：(1)心內膜炎，常見的病原菌為viridans streptococci 或 Staphylococcus aureus，(2)化膿性肺炎，(3)右向左分流(right-to-left shunt)的先天性心臟畸形，例如：法洛氏四合症(tetralogy of Fallot)、開放性動脈導管、心房心室中膈缺損，右向左的血液分流引起的動脈血氧降低及紅血球增加，可能會造成腦組織局部缺血，未被肺微血管網過濾的微生物因而適於繁殖，易形成膿瘍，(4)肺動靜脈畸形；3. 因手術或創傷引起的感染；4. 約25%的腦膿瘍無法找到明確的感染途徑。[1]
肺動靜脈畸形為未經微血管，直接連接肺動靜脈的不正常血管連結，肺動靜脈畸形的盛行率約為2~3/100,000。女性多於男性(男：女=1：1.5 ~ 1.8 )。80~95%的肺動靜脈畸形是由遺傳性出血性毛細血管擴張症(hereditary hemorrhagic telangiectasias，Osler-Weber-Rendu syndrome)引起，後天肺動靜脈畸形比例較低，其可能的成因有：創傷、肝硬化、惡性腫瘤等。[2] 肺動靜脈畸形的臨床症狀有低血氧、紅血球增多症、杵狀指(clubbing fingers)、直立型低血氧，但單一且小於兩公分的動靜脈畸形不常造成上述症狀。肺動靜脈畸形的併發症主要為中風及腦膿瘍，未經治療的肺動靜脈畸形患者50%會有上述併發症，但治療能將併發症降至3%。目前治療是以經動脈血管栓塞為主流，復發率約5~19%，而手術治療適用於急性出血或無法接受血管栓塞的病患。[3] 為預防肺動靜脈畸形引起腦部感染可給予amoxicillin/clavulanate，若對penicillin類抗生素過敏，可改用clindamycin。[4]
遺傳性出血性毛細血管擴張症是引起肺動靜脈畸形最常見的原因，約50%遺傳性出血性毛細血管擴張症患者合併有肺動靜脈畸形。有家族史，或有鼻出血、毛細血管擴張等症狀，應將遺傳性出血性毛細血管擴張症列入鑑別診斷。[4] [5]
目前腦膿瘍的治療以外科引流結合高劑量靜脈注射抗生素為主，但找出並治療引起腦膿瘍的原因，才能避免反覆感染及相關併發症。
[參考文獻]
- Harrison's Principles of Internal Medicine 18th Edition
- Cartin-Ceba R, et al. Pulmonary arteriovenous malformations. Chest 2013;144:1033-44.
- Lon A. Walder, DO et al. Pulmonary arteriovenous malformations with brain abscess. Am Heart J 1994;127:227-32.
- Mathis S. et al. Cerebral abscesses in hereditary haemorrhagic telangiectasia: A clinical and microbiological evaluation. Clinical Neurology and Neurosurgery 2012;114:235-40.
- Shovlin CL. Hereditary haemorrhagic telangiectasia: Pathophysiology, diagnosis and treatment. Blood Reviews 2010;24:203-19
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Case Discussion
繼續教育考題