Preparation for Surgery for Cavernous Malformations in Children

Indications for Procedure

• Indications for embarking on treatment: See Candidate selection for surgery, below.
• Timing of intervention – varying recommendations: There is no consensus about the timing of surgery for patients who have suffered a hemorrhage. Some recommend waiting for 4 weeks to allow neurological recovery and stabilization of the lesion (61). Others suggest operating in the subacute period (2–3 weeks) because the presence of fresh hemorrhage facilitates surgical dissection (19).

Candidate selection for surgery

• Asymptomatic: Patients with asymptomatic cavernous malformations can be managed with observation and MRI follow-up.
• Symptomatic with seizures: Patients with cavernous malformations who present with seizures should be treated initially with anticonvulsants. Surgical intervention is considered if seizures are not satisfactorily controlled with pharmacotherapy, if the adverse effects of the antiepileptic drugs are too severe, or if the patient complies poorly with the therapeutic regimen (3). Some authors recommend surgery for all symptomatic supratentorial lesions (7).
• Symptomatic with hemorrhage: In general, surgery should be considered for cavernous malformations with symptomatic hemorrhage. The decision should take into account the location of the lesion in terms of eloquent area, supra- or infratentorial, and relation to the pia or ependymal surface.
• Klopfenstein criteria for operating on brainstem cavernomas: Resection of a brainstem cavernous malformation can be considered if one of four criteria is met: (a) the lesion abuts the pial to ependymal surface or is exophytic, (b) the lesion has produced multiple hemorrhages causing progressive neurological deficits, (c) the acute hemorrhage extends outside the lesion capsule, and (d) there is significant mass effect from a large intralesional hemorrhage (29).
• Recurrent hemorrhage as an indication for operating on brainstem caveromas: Brainstem cavernous malformations that cause two or more hemorrhage events are likely to follow an aggressive course, and thus these lesions should be strongly considered for microsurgical resection (3). It should be emphasized that each situation is unique, and patients must be treated individually on the basis of their clinical history, the location of the lesion, and the technical expertise of the surgeon.
• T1-weighted MRI preferred for planning: To judge the relationship between the lesion and the brain surface, T1-weighted MRI sequences should be used because of the blooming artifact of hemosiderin on T2-sequences.

Preoperative Orders

• Functional MRI: fMRI for functional mapping can be a useful adjunct for planning to minimize neurological deficit.
• Anticonvulsants: For patients with epilepsy who are undergoing awake craniotomy and brain mapping for excision of the carvenours malformation, additional doses of anticonvulsants before or during the operation may be needed to minimize the risk of intraoperative seizure.

Anesthetic Considerations

• Discuss need for IOM: The anesthesiologist plays an important role in intraoperative neurophysiological monitoring by limiting the effect of muscle relaxants before electrical stimulation for motor responses, taking precautions to avoid complications from motor evoked potentials such as tongue-bite, and using appropriate anesthetics to facilitate the signal pick-up of SSEPs.
• Discuss need for ECoG: In select cases, intraoperative functional mapping and/or electrocorticography is needed. General anesthesia may be used or an awake craniotomy for the mature adolescent. Detailed preoperative discussion with the anesthesiologist and close cooperation are needed.

Devices to Be Implanted

• Electrodes for ECoG: For epilepsy surgery, intracranial electrode implantation may be required. The implantation scheme should be well planned before the operation.

Ancillary/Specialized Equipment

• IOM: IOM can be useful when operating on lesions near motor or sensory pathways, particularly when they are within the brainstem.
• Intraoperative ultrasound: Ultrasound can be useful when approaching deep-seated cavernomas.
• Operative microscope