Paediatric midbrain abscess: A case report and literature review

Epidemiology

Twenty-four cases of paediatric brain-stem abscess have been described in the literature, with the first case reported in 1974. Midbrain and medulla oblongata were second and third places, respectively, only seven patients had an abscess that involved more than one part of the brain-stem. Risk factors were found in 56–86% of paediatric patients. Brainstem abscesses are usually spread by a haematogenous route from a distant primary site of infection (e.g., heart or lung) or a local infection (e.g., dental, otogenic infection, or meningitis).^[16] Sinusitis was not associated with brain-stem abscesses because abscesses due to sinusitis are localised in the frontal lobe.^[12] Congenital heart disease was the most common non-infectious risk factor, and other non-infectious risk factors included immunodeficiency and neurosurgical procedures.^[17] Cryptogenic brain abscess is defined as when the primary source of infection cannot be identified. Ten of 25 patients had a cryptogenic abscess (40%).

Clinical presentation

The clinical presentation of a brain abscess includes headache, fever, and neurologic deficits.^[13] Headache is the most common symptom of a brain abscess, followed by fever. Neurologic deficits in midbrain abscess manifest as cranial nerve palsy or hemiparesis.^[18] Facial (VII) and abducens palsy (VI) were the most commonly affected nerves. However, all cranial nerves may be affected except for the hypoglossal nerve (XII). Altered consciousness in the form of somnolence was observed in all patients, but coma did not occur. Seizures occur in half of the patients with a brain abscess but in only one of the patients with a brain-stem abscess.^[19]

Diagnosis

Management

The establishment of a guideline for the management of brain-stem abscesses is not yet well described, as there are few paediatric patients who have been treated for this type of central nervous system infection. Therapeutic management includes a mandatory drug component in the form of antibiotics and a neurosurgical component that should always be considered but cannot be performed in some cases. There is no risk-free formula for performing such surgery; even with the minimally invasive technique, stereotactic or neuro-navigation-assisted surgery is considered safer and more beneficial compared with open craniotomy, although there is no argument for the superiority of any surgical procedure. However, the goal remains the same, which is to assess the nature of the lesion by biopsy if the diagnosis cannot be fully confirmed preoperatively and to perform aspiration of the pus to reduce the volume of the abscess and achieve immediate relief, which allows better penetration of antibiotics and an increase in their concentration, improving the efficacy and extent of antimicrobial treatment. The surgical approach allows for assessing the microbiology of the lesion, minimising the number of pathogens, and rupturing the abscess capsule.^[23] Patients with a focal neurologic deficit at admission (87.5%) or presenting clinical decline or else a growth display in radiological control^[24] should always be considered to undergo surgical treatment to decrease the mass effect on the brain-stem. However, fatal complications can always occur, like the menace of intra-ventricular rupture and bleeding from the abscess capsule.^[5] Once the diagnosis of brain-stem abscess is made, empiric antibiotics that include a broad spectrum covering Gram-positive, Gram-negative bacteria and anaerobes, an antibiotic with better penetration through the blood-brain barrier such as cephalosporins with metronidazole, should be administered intravenously and antibiotic therapy should then be adjusted according to the antibiogram of the positive culture.^[22,25] For at least 6–8 weeks of treatment time, eventually after spotting the vanishing cavity on the brain MRI. The management of the brain-stem abscess should solidly include identifying the source of infections and curing it. Arlotti et al. suggest antibiotic therapy only. In patients who have a Glasgow Coma Scale >12, a small abscess at least 2.5 cm in diameter, multiple abscesses, or culture from other sources (CSF/blood).^[26] Jamjoom suggested conservative treatment in children who are in stable clinical conditions and who can be monitored by imaging. Publications on this topic show that standard craniotomy was performed in 14 patients (56%), antibiotics only in seven patients, including our patient (28%), and stereotactic abscess aspiration in four patients (16%). Both standard craniotomy and stereotactic aspiration showed good results, safety, and immediate clinical improvement without surgical complications, so we believe that the use of a surgical procedure should always be considered. Further studies need to be performed to evaluate which surgical procedure is most efficient in these patients.

Prognosis

In a recent analysis of brain-stem abscesses, improvement was noted in 80.0% of patients, with complete resolution of symptoms in 36.0%. Incomplete neurologic recovery was seen in 44.0% of the total group; mortality was estimated at 12.0%. In conclusion, the prognosis for brain-stem abscesses is good and almost similar to the entire group of brain abscesses, considering that significant disability at follow-up was almost not described. As described in the literature on brain abscesses, no neurologic deficits or only minor sequelae are reported in only 70% of cases. Nevertheless, the pathology remains a serious condition associated with high morbidity.^[14,22]