Page 473 - ILAE_Lectures_2015

Chapter 49

Outcome of surgery

MATTHEW C. WALKER and DAVID R. FISH

UCL Institute of Neurology, National Hospital for Neurology and Neurosurgery, Queen
Square, London
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The successful outcome for epilepsy neurosurgery depends upon:

 type of operation
 site of the lesion
 nature of the lesion
 results of pre-operative assessment (especially the degree of congruence)
 experience of the centre/surgeon carrying out the surgery.

The risks depend upon these factors, but the risks of any additional investigations also need
to be incorporated (e.g. the risks of intracarotid amytal, depth electrodes etc).

Risks of pre-operative investigation

Even apparently non-invasive investigation can carry some risk. Video-EEG telemetry can
carry some risk if drug reduction is undertaken in order to record an adequate number of
seizures. Drug reduction can produce more severe seizures that can occasionally result in
post-ictal psychosis, peri-ictal injury and, rarely, death. Thus consent is necessary for drug
reduction in video-EEG telemetry units with the potential risks and benefits carefully
explained to the patient.

Invasive investigations carry more obvious risks:

 A standard intracarotid sodium amytal test results in permanent neurological change
in less than 0.5%, but transient neurological deficits can occur in more (up to 3%).

 Subdural electrodes frequently result in mild-to-moderate complications. The risk of
infection is approximately 3–5%; over a quarter of patients develop an aseptic
meningitis – usually restricting recordings to 10 days or less.

 Intracranial electrodes are mainly complicated by infection and haematoma. The risk
is dependent on the number of depth electrodes and their placement. The risk is
approximately 1–2% for most studies.

Outcome of operation by type of surgery

Temporal lobe surgery (anterior temporal lobectomy, selective amygdalo-hippocampectomy)
results in approximately 70% of patients becoming seizure free (this figure may be even
higher in those with hippocampal sclerosis and concordant investigations), and 20% are
improved. Approximately 50% of patients remain seizure free for 10 years. The overall
mortality of temporal lobectomy is less than 0.5%, and the risk of permanent hemiparesis less
than 1%. A transient hemiparesis can occur in up to 5%. Memory problems and visual field
defects are other common complications. Visual field defects that prevent driving can occur
in over 5% of those undergoing mesial temporal resection. Psychosis and depression are not