Preparation for Surgery for Brain Abscesses in Children
Indications for Surgery
Abscess >2.5 cm: In one series looking at the outcome of patients who were medically managed (too ill for surgery), those for whom medical treatment failed had abscesses that were 2–6 cm in diameter (mean 4.2 cm). A cutoff size of 3 cm was suggested, with those patients having abscesses > 3 cm being recommended for surgical management (128).
Condition pending immediate deterioration: Patients exhibiting signs of intracranial hypertension referable to a mass effect from the abscess or a risk for intraventricular rupture are usually managed surgically. Alterations in the LOC may herald impending herniation and should prompt surgical drainage of the abscess to alleviate mass effect (30, 40). Intraventricular rupture of an abscess, evident due to hydrocephalus and enhancement of ventricular walls, requires urgent surgical debridement, ventricular drainage, and intraventricular and systemic antibiotic treatment (30, 114).
Abscesses with associated foreign material: Trauma patients with post-traumatic wounds overlying the abscess or whose scans show fragments of bones or foreign material adjacent to or within the abscess are usually managed surgically to insure removal of any non-vital, colonized material that could serve as a continuing source for infection (30).
Failure of medical management: Progressive improvement in imaging is expected after the initiation of antibiotic treatment. It takes 1–4 weeks (mean 2.5 weeks) for imaging studies to show a decrease in size of the lesion (60). By 1 month 95% of lesions that can be managed medically will decrease in size (60). Surgery is usually performed when there is a failure to see the expected response to medical treatment.
Mycotic infections: Fungal infections of the CNS are almost always a clinical surprise. Their presentation is subtle, often without any diagnostic characteristics, and they are frequently mistaken for pyogenic abscess or brain tumor. Granulocytopenia, cellular and humoral mediated immune dysfunction are predisposing factors to the development of CNS infections in immunosuppressed patients. Mycotic infection should be considered in cases manifesting with brain abscess signs and symptoms, especially in immunocompromised hosts. Aggressive neurosurgical intervention for surgical removal of abscesses, granulomas, and focally infracted brain; correction of underlying risk factors; and medical antimycotic treatment of the source of infection should form the mainstay of management (143).
Neonates require early intervention: Early aspiration is advocated in infants because of the propensity for early seizures with meningitis and hydrocephalus, all of which portend a poor prognosis (30).
IVF rate: Rate is standard for maintenance of normovolumia.
Antibiotic: Order per infectious disease consultant’s recommendations.
Routine: In most patients general anesthesia is used for the sake of patient, although mild sedation and local anesthesia can be considered in medically ill patients.
Devices to Be Implanted
EVD for access to CSF for medication and drainage: In cases of acute hydrocephalus due to obstructed CSF flow, an EVD should be inserted. When intraventricular rupture of the abscess does occur, an EVD can be inserted for the instillation of antibiotics.
Stereotaxic aspiration: A stereotaxic frame should be available if a frame-based aspiration is planned. A computer-assisted neuronavigation apparatus should be available if a frameless stereotactic aspiration is planned.
Neuroendoscopic equipment: A rigid or flexible neuroendoscopic system with working and/or irrigation channels should be available if a need for their use is anticipated.
Surgical microscope: Especially in trauma patients with post-traumatic wounds overlying the abscess or whose scans show fragments of bones or foreign material adjacent to or within the abscess, it is better to use microsurgical technique via craniotomy.
Material for anaerobic culture samples: Material for anaerobic culturing of specimens obtained during surgery should be available, given the high incidence of anaerobic organisms in brain abscesses.