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Year : 2000  |  Volume : 48  |  Issue : 3  |  Page : 272--5

Brainstem abscess complicating tetralogy of Fallot successfully treated with antibiotics alone.

JD Pandian, NV Moosa, PJ Cherian, K Radhakrishnan 
 Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, Kerala, 695011, India., India

Correspondence Address:
J D Pandian
Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, Kerala, 695011, India.
India

Abstract

Medically treated brainstem abscess in a 11 year old boy with tetralogy of Fallot is reported. There was a complete resolution of the lesion without any neurologic sequelae during parenteral antibiotic therapy with crystalline penicillin, chloramphenicol and metronidazole. The pathogenesis and management of cardiogenic brain abscesses in general and brainstem abscess in particular has been reviewed.



How to cite this article:
Pandian J D, Moosa N V, Cherian P J, Radhakrishnan K. Brainstem abscess complicating tetralogy of Fallot successfully treated with antibiotics alone. Neurol India 2000;48:272-5


How to cite this URL:
Pandian J D, Moosa N V, Cherian P J, Radhakrishnan K. Brainstem abscess complicating tetralogy of Fallot successfully treated with antibiotics alone. Neurol India [serial online] 2000 [cited 2020 Aug 6 ];48:272-5
Available from: http://www.neurologyindia.com/text.asp?2000/48/3/272/1522


Full Text




  ::   IntroductionTop


Brainstem abscess (BSA) is a rare but extremely dangerous variety of suppurative disease. Solitary BSA constitute only 0.5 to 6 % of the total reported cases of brain abscesses.[1] The BSAs are generally believed to have a poor prognosis. The diagnosis and prognosis of BSA have recently undergone a remarkable change because of the advent of computed tomographic (CT) scan, magnetic resonance imaging (MRI) and improved medical and surgical therapies.[2] To the best of our knowledge, there are only nine reports of immunocompetent patients with BSA successfully treated with medical therapy alone.[3],[4]

The incidence of brain abscess in the population with congenital heart disease (CHD) varies from 5 to 18.7%.[5] Despite improvements in imaging techniques and surgical and medical management with newly developed antibiotics, the mortality rate for brain abscess associated with cyanotic CHD continues to be over 13% even in the CT era.[6] BSA in patients with cyanotic CHD has rarely been reported.[7],[8] There is only a single documentation of a cardiogenic BSA successfully treated by antibiotic therapy alone.[7] We report the successful medical management of a BSA in a young boy with tetralogy of Fallot.




  ::   Case reportTop


A 11 year old boy who was dignosed to have a cyanotic CHD in the late infancy was admitted to the Neurology section of Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, with the symptoms of low grade fever, headache, drooping of the left eye and unsteadiness of gait. Ten days prior to hospitalisation, he developed fever, occipital headache and vomiting. Two days later, he developed left sided ptosis and binocular diplopia on horizontal gaze. Within the next few hours he became unsteady, and swayed to his right. His paediatrician diagnosed a brainstem stroke and referred him to this hospital.

General physical examination revealed an afebrile patient with conjunctival congestion, central cyanosis and clubbing of digits in all four limbs. Cardiac examination showed an ejection systolic murmur over the left second intercostal space close to the sternum and a single second heart sound. There were no peripheral signs of infective endocarditis. Neurologically, he was alert and well-oriented. He had partial ptosis, a dilated sluggishly reacting pupil, and restricted elevation and abduction involving the left eye. The optic fundi showed no papilloedema.An upper motor neuron type of facial weakness and an upgoing plantar response, with normal tone and power of limbs was noted on the right side. Incoordination of right upper and lower limbs was evident and he swayed to the right on walking. His neck was supple and Kernig's sign was absent.

Laboratory examination revealed polycythaemia with a packed cell volume of 68%, leukocyte count of 9200/mm[3] with 64% neutrophils. Echocardiography confirmed the diagnosis of tetralogy of Fallot. No vegetations were seen. CT scan of the head showed a contrast enhancing 'Figureure-of-eight' shaped lesion in the left side of the midbrain, extending into the upper pons [Figure.1a]. There was perilesional oedema with pressure effect on the third ventricle and the quadrigeminal plate cistern.

A diagnosis of brainstem abscess was made and the patient was started on intravenous crystalline penicillin, chloramphenicol and metronidazole along with dexamethasone. The child continued to have spikes of fever initially but became afebrile by the third day. Serial blood cultures were sterile. The third nerve paresis recovered completely by the seventh day of hospitalisation. He had minimal residual ataxia when he was discharged after 2 weeks of hospital stay. On follow-up, after six weeks of parenteral antibiotic therapy from a local hospital, he did not have any residual neurological deficit. A repeat CT scan showed complete resolution of the BSA [Figure.1b]. The patient was referred for cardiac surgery.




  ::   DiscussionTop


BSAs are generally believed to have a poor prognosis. This is primarily because of their anatomic location which can lead to catastrophic complications, frequently precluding surgical drainage.[9] It has been advocated that, in patients with a solitary BSA, prompt surgical intervention is indicated to prevent mortality and further morbidity.[10] However, nine previously reported cases in the literature suggest that medical therapy should be considered as a reasonable first option.[3],[4]

Our patient is the fourth case of BSA reported among patients with CHD and the second medically successfully treated BSA [Table I]. It is wellrecognized that patients with cyanotic CHD are prone to develop brain abscesses. Tetralogy of Fallot is the most common cyanotic CHD associated with intracranial suppuration.[12],[13],[14] The abscesses are most often located in the supra-tentorial compartment. Only 4% of patients had posterior fossa abscesses in a series of 75 cardiogenic abscesses[12] but none had BSA. The prognosis of a cardiogenic abscess is worse than that of other brain abscesses, and mortality rates have ranged from 27.5% to 71%.[12] Thus a combination of a BSA and a cyanotic CHD in a patient has serious implications. In the brainstem, pons is the most common site of the abscess. The midbrain is involved less often and medullary abscesses are distinctly rare.[8] Most of the abscesses occupy one or two segments of the brainstem, the pons and midbrain being a frequent combination as was seen in our patient.[8]

The lungs and the teeth have been found to be the most common source of the suppuration and account for 34 to 57% of cases.[15] Contiguous spread of infection from the ears is the next common source. The most frequently isolated organisms in BSA are Streptococcus and Staphylococcus species with other Gram negative and anaerobic bacteria accounting for most other cases.[1] Mycobacterium tuberculosis is a common cause of BSA, particularly in regions where pulmonary tuberculosis is widely prevalent.[3],[4] Various other organisms such as Haemophilus, Proteus and Bacteroides have been isolated from these abscesses.[2] Of the four cases of BSA in cyanotic CHD patients reported in the literature, causative organisms could be identified in two, non-haemolytic streptococci being the pathogen in both [Table I].[8],[11] An empirical antibiotic regimen to cover this organism would be appropriate in such cases, if the causative organism cannot be isolated. The dramatic response to the penicillin, chloramphenicol and metronidazole regimen in our patient probably exemplifies this.

Various factors play a role in the pathogenesis of brain abscess in patients with cyanotic CHD. The filtration of the blood through the pulmonary circulation, where bacteria are intercepted by phagocytosis, is bypassed via an intracardiac right to left shunt. This may allow direct entry of the organisms to cerebral circulation.[5],[12],[14] In addition, in these patients, the brain may also have minute low-perfusion areas due to increased blood viscosity resulting from compensatory polycythaemia leading on to tissue hypoxia and metabolic acidosis.[5] Shunted blood containing microorganisms may be seeded in such areas, forming a cerebral abscess.

Presently, neurosurgical aspiration or excision of BSA can be performed under direct observation using the operating microscope, or aspirated and biopsied with CT or MR guided stereotaxy.[8],[10],[16] Advantages of surgical interventions are that they are therapeutic and also provide pathological and bacteriological proof of an infectious process. However, positive microbiological identification was possible in only three out of [eight] patients in a series of BSA treated with stereotaxic biopsy and drainage.[10] Total excision of the BSA has rarely been possible because of the elongated nature of these abcesses and the difficulty in accessing the area of the brainstem in which they are located.[17]

Management of brain abscess among cyanotic CHD patients poses special problems. These patients possess not only cardiopulmonary risk but a wide variety of coagulation defects. Together, these factors increase the risk of anaesthesia and surgery.[5],[6],[18],[19] There is considerable controversy regarding the choice of medical versus surgical therapy in patients with cardiogenic BSA. Surgery seems to be preferred by most authors because of the ability to establish the diagnosis, obtain a specimen for culture and above all to reduce the mass effect responsible for progressive neurological deterioration.[8],[10] Medical therapy alone is recommended in the case of a neurologically stable patient with a highly presumptive diagnosis of an abscess smaller than 2 cm when continuous CT monitoring is available. At the first sign of neurological deterioration or enlargement of the abscess, surgery must be undertaken.[2]

Among the three patients (including ours) who survived with CHD and BSA, only one with a large abscess (3.2cm) was successfully treated by CT guided stereotaxic surgery [Table I].[8] In the remaining two patients, including the current case, BSA disappeared with medical therapy alone.[7] In our patient, stereotaxic aspiration was deferred owing to the relatively smaller size of the lesion (<2cm). Repeat serial scans to monitor the therapy were not performed because of economic constraints. Though this patient had significant oedema in the brainstem and the thalamus, antioedema treatment with diuretics was avoided in this patient with tetralogy of Fallot as it produces dehydration and increases the haemoconcentration further. Our patient received a course of dexamethasone for two weeks to reduce the oedema. The optimal length of antibiotic therapy for BSA has not yet been determined. Most of the patients described in the literature, who survived, received 6 to 12 weeks of antibiotics. The duration of antibiotic treatment is dictated by clinical response and by serial imaging studies.[17]

In conclusion, the management of a solitary BSA in CHD should be individualised to each patient. Medical therapy alone is recommended in a stable patient with a CT/MRI diagnosis of BSA. At the first sign of deterioration or when there is no response to medical treatment within two weeks, surgery may be undertaken, preferably by CT guided stereotaxic aspiration.



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