UNCOMMON INTRACRANIAL ABSCESSES

Abstract

Background:

Intracranial abscess, though uncommon, have relatively higher occurrence in low socio-economic settings where previous antibiotic abuse and lack modern culture techniques makes isolation of organisms difficult. Diagnosis and treatment are further delayed by a poor referral system and low index for suspicion. Tuberculoma, cannabis abuse, ventriculo-peritoneal shunt catheters and cancer therapy are presented here as unusual causes of intracranial abscesses.

Aims & Objectives

To highlight less commonly encountered causes of an uncommon, but dreaded, neurosurgical condition, their diagnosis and treatment approaches.

Case Reports:

Five patients who had surgical evacuation of intracranial abscesses not due to pathology from the more familiar spread from sinusitis, mastoid, middle ear, post-meningitic or post -traumatic aetiology are presented. Contrast computerised tomography (CT) brain scan was essential in clinching the diagnosis and determining the management options.Conclusions: Persistent headaches or features of intracranial involvement (in patients undergoing treatment for other conditions) should always warrant CT of the brain. However, there are several differential diagnoses of ring-enhancing lesions on CT which have to be excluded when considering an abscess.

Introduction

Intracranial abscesses are rare and potentially fatal 1. Infections from the paranasal sinuses as well as mastoid, middle ear, post-meningitic and post-traumatic infections account for the aetiology and may be complicated by sinus thrombosis, ventriculitis and hydrocephalus with shunt complications from bacterial as well as fungal abscesses 1,2,3.

In this study five patients with uncommonly encountered types of intracranial abscesses who were managed at the University of Benin Teaching Hospital, Nigeria, are presented to highlight the diagnostic value of contrast CT brain scan and a high index of suspicion.

Case Reports

1: A 36- year old male presented via the Accidents and Emergency department with a 2-month history of generalized headaches, difficulty with walking and a one-week history of deteriorating of level unconscious. He had undergone insertion of a ventriculo-peritoneal shunt (VPS) at another Teaching Hospital three decades earlier, as a child, for congenital hydrocephalus. He also had generalized tonic clonic seizures.

Physical examination showed an acutely ill young man with a right frontal VPS and a Glasgow Coma Score (GCS) of 11. He had spastic quadriparesis with normal pupil size. Meningeal signs were absent.

Computed tomography (CT) scan of the brain showed the VPS catheter tip within the right frontal horn, effaced lateral and third ventricles and bilateral frontoparietal ring contrast-enhanced crescentic collections.

The diagnosis made was bilateral subdural empyema from secondarily infected subdural haematomas the latter resulting from chronic shunt overdrainage.

Cerebrospinal fluid (CSF) was clear and colourless fluid with no evidence of shunt infection. He underwent bilateral frontal and parietal burrholes with evacuation of inspissated pus. No shunt replacement was necessary. Culture yielded no organism.

He was discharged on the 10^th postoperative day. He has remained well for two years.

2. An 11- year old male was referred from a General Hospital with a two-year history of left upper and lower extremity weakness, 6-month history of right parietal headaches with recurrent left-sided focal seizure. There was no background history of seizure disorder from early childhood. He had been having treatment at home, self-medicated by parents, with antibiotics and anticonvulsants (sodium valproate, phenytoin sodium, and carbamazepine) to which he was unresponsive.

Physical examination showed a chronically ill young male with a GCS of 15. He had dysgraphaesthesia and spastic left hemiparesis; pupils were 5mm and sluggishly reacting. Chest, cardiovascular and abdominal examinations were normal.

CT scan of the brain showed a massive right parieto- occipital hypodense spherical mass with a thick ring contrast-enhanced capsule which abutted on the falx cerebri medically and the parietal bone laterally. There was effacement of the (ipsilateral) lateral and third ventricles and the Sylvian fissure with midline shift to the left side (figure 1).

Chest radiographs, complete blood counts and biochemistry were normal; erythrocyte sedimentation rate was raised, but Mantoux test was normal. A diagnosis of right parieto-occipital intracerebral abscess was with imminent tentorial herniation was made.

He underwent a limited (5cm diameter) craniectomy under local anaesthetic infiltration with evacuation 150ml of thick greenish-yellow non-foul pus.

Clinical condition improved and culture was negative. He slowly deteriorated within a week; repeat CT show a massive recurrence which was drained by bedside needle aspiration though the craniectomy; a second re-accumulation in 10 days with neurological deterioration was again confirmed with CT and evacuated by a second bedside needle aspiration. A third re-accumulation was confirmed for which the patient underwent a right parieto-occipital craniotomy with decortication. The excised capsule was thick, thick and riddled with caseating granulomas (figures 2 and 3). Histology confirmed Tuberculoma. He had six weeks of intravenous ceftriazone; he was also commenced on anti-tuberculous and anticonvulsant therapy, with physiotherapy. He has remained well without recurrence and is seizure-free on anticonvulsants. He is still having antituberculous treatment and out-patient chemotherapy for residual hemiparesis.

3. A 15-year old male presented with a 4-week history of persistent right frontal headaches. There was no history of previous head trauma, or sinus, ear or chest infection. He admitted to a three-year use of cannabis in the boarding school which had continued at University.

Physical examination showed a healthy looking young man with a GCS of 15 and normal mental state, Cranial nerve and meningeal examination. H e had a subtle right hemiparesis with exaggerated muscle stretch reflexes.

Laboratory examinations and chest radiographs were normal.

CT scan of the brain showed a right frontal ring contrast-enhanced hypodense biconvex lesion. There was associated perilesional oedema with effacement of the right frontal lobe.

A diagnosis of right frontal extradural empyema was made. Full blood counts and ESR were normal. Retroviral screening and Mantoux tests were normal. Otolaryngologic assessment showed no abnormality.

He underwent a right frontal burrhole evacuation under general followed by intravenous ceftriazone for 6 weeks. He was jointly managed with Psychiatry.

He has had no recurrence in three years.

4. A 45-year old female, referred by the general surgical unit, who had been on treatment for carcinoma of the right breast for a year. She was receiving the sixth course of cytotoxic chemotherapy. She complained of left frontal headaches and had right-sided focal seizures. She had received two unit of blood transfusion for anaemia.

Physical examination showed a pale, middle-aged woman with normal mental state, cranial nerves and meninges; long tract examination was normal.

Laboratory examination showed pancytopaenia. CT scan of the brain showed a left frontal hypodense ring contrast –enhanced intracerebral lesion with perilesional oedema.

The diagnosis made was left frontal intracerebral abscess to rule out cerebral metastasis.

She was worked up for diagnostic burrhole biopsy and/or evacuation of abscess. Aspiration yielded 80 ml of pus. Culture was negative. She had intravenous ceftriazone for six weeks. She remained neurologically normal after one year follow up.

5. A 71-year old male referred from the Otolaryngology unit a year after the diagnosis of advanced carcinoma of the larynx and had undergone radiotherapy. He was referred with seizures and deteriorating level of consciousness.

Physical examination showed a chronically ill elderly man. He had a tracheostomy tube in-situ. GCS was 8 and he had spastic left hemiparesis.

CT scan of the brain showed right parieto-occipital hypodense ring contrast-enhanced biconvex mass and a right parietal intracerebral hypodense ring contrast-enhanced mass. The lateral and third ventricles were effaced with shift of the midline to the left. The diagnosis made was right parieto-occipital extradural empyema with a right parietal late cerebritis lesion - to rule out metastases - in a patient with advanced carcinoma of the larynx.(Figure 4)

He had a right parietal burrhole evacuation of 150mls extradural abscess. He continued to deteriorate and died after 48 hours.

Conclusions

An intracranial abscess, though uncommon, may complicate a number of clinical conditions. A high index of suspicion and prompt CT scan request for the patient who has vague symptoms of CNS involvement expedites diagnosis and reduces the poor outcomes due to delayed diagnoses.

Discussion

Unusual presentations of intracranial abscesses in literature include subdural empyema associated with CSF shunts, intracerebral abscess due to tuberculosis, brain abscess in drug abusers and multiple intracranial abscesses in immune suppressed patients (such transplant patients and those undergoing various treatments for cancer)4,5,6,7. Even in countries where tuberculosis is endemic, intracranial tuberculous abscesses are uncommon6. Howbeit, central nervous system involvement is one of the most devastating clinical manifestations of tuberculosis.

Because these are unusual complications and presentations of an uncommon clinical entity, frequent delays in making the diagnosis, reluctance in carrying out early CT scan of the brain - either for financial reasons or non-availability - and lack of an index of suspicion, render these conditions a significant challenge to the clinician2.

Due to the widespread use of parenteral hyperalimentation, aggressive chemotherapy, corticosteroids and other immunosuppressive therapies as in transplant patients, and owing to increasing intravenous drug abuse, there is increased risk of opportunistic infections, especially candida albicans than in years past8. Fungal brain abscesses are not commonly reported here, but should be suspected in patients on cancer treatment and drug abusers.

The most important factor influencing the outcome of these unusual presentations of intracranial abscesses include early CT diagnosis, high index of suspicion, prompt surgical decompression and complete course of appropriate antibiotic or antifungal therapy2,9. In cerebral tuberculosis, imaging, tissue diagnosis by histopathology, HIV testing and antituberculous treatments are essential10. Common differential of multiple, small ring-enhancing lesions on CT to be borne in mind include candida albicans, staphylococcus aureus, tuberculosis, metastases and multiple sclerosis.

While the mortality for intracranial abscesses is reducing - as low as 3% - that in patients with unusual presentations and complications may be higher than 90%; this is due to delayed diagnosis, unusual causative organisms, poor penetration of antifungals into the central nervous system (CNS), associated cerebral infarction, vascular invasion, ventriculitis, meningo-encephalitis, endocarditis and systemic disease4,7,9.

Figure 1:

CT brain scan in an 11-year old showing massive right parietal intracerebral abscess

Figure 2:

Intraoperative appearance of the tuberculous mass for the patient in figure 1 with multiple granuloma

Figure 3:

Cavity of the tuberculous abscess

Figure 4:

CT brain scan of a 71-year old man with laryngeal carcinoma with right parietal extradural empyema and intracerebral abscess