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of course, a reduction of seizures. An older child in normal school is more likely to be seeking
seizure freedom and a greater independence. Other associated issues must also be addressed,
such as behaviour and any realistic appreciation of change that is unlikely to be predictable.
A contract between the professionals and family is desirable prior to the surgical decision.

Outcome

Outcome of epilepsy surgery should be measured not only in terms of seizure freedom, but
also in terms of development, neuropsychology, behaviour and quality of life7. Seizure
freedom is quoted most often in outcome studies no doubt as it is the easiest to determine.
Large post-surgical series have shown seizure freedom in 4087%12-14 (Table 1) related more
to the underlying pathology than age at onset of seizures, age at surgery, duration of epilepsy
or procedure performed, with better outcome seen with acquired as opposed to developmental
pathology. Medication reduction is often an aim of parents, and cannot be guaranteed. Around
50% are successfully weaned from AEDs; a recent European collaborative study
demonstrated an early wean did not provoke a recurrence that was not inevitable18.

With focal resection, the degree of epileptogenic tissue removed is a major determinant of
seizure outcome, although the degree to which this can be achieved is also related to the
underlying pathology. There is some evidence that the outcome following surgery for
developmental lesions may deteriorate with time, that is the likelihood of seizure freedom is
less in the longer as opposed to the short term, but that outcome with such lesions may be
better with earlier surgery14. The lesser likelihood of seizure control however does not
preclude consideration, providing the aims of surgery are realistic and clearly identified
preoperatively. Many children are also likely to achieve a substantial reduction in seizure
frequency13-15 with a reduction in anticonvulsant requirement.

Developmental outcome has been reported as improved following surgery in many studies
but has been difficult to quantify, particularly in the very young, as outlined above. As a
consequence it is important to obtain as much information as possible about the nature of the
epilepsy and the procedure planned, with clear outcome aims clarified with the family.

It is for this reason that a system of categorisation of epilepsy surgery on the basis of the
probability of success has been proposed11. This would divide between those in which
techniques and prognosis are well established (e.g. conventional temporal lobectomy and
hemispherectomy for acquired lesions), those in which prognosis is not so clear-cut (e.g.
extratemporal resections, hemispherectomy for developmental lesions, certain temporal
lobectomies), and procedures performed on highly problematic individuals in whom surgical
intervention may help (e.g. callosal section, subpial transection, trials of partial resection of
abnormal tissue).

References

1. DAVIDSON, S. and FALCONER, M.A. (1975) Outcome of surgery in 40 children with temporal lobe epilepsy.
Lancet i, 1260-1263.

2. OUNSTED, C., LINDSAY, J. and RICHARDS, P. (1995) Temporal Lobe Epilepsy 1948–1986. A Biographical
Study. Mackeith Press, Oxford.

3. KWAN, P., ARZIMANOGLOU, A., BERG, A. et al (2010) Definition of drug resistant epilepsy: consensus
proposal by the ad hoc Task Force of the ILAE Commission on Therapeutic Strategies Epilepsia 51, 1069-1077

4. LODDENKEMPER, T., HOLLAND, K.D., STANFORD, L.D. et al (2007) Developmental outcome after
epilepsy surgery in infancy Pediatrics 119, 930-935.

5. FREITAG, H., TUXHORN, I. (2005) Cognitive function in preschool children after epilepsy surgery: rationale
for early intervention. Epilepsia 46, 561-7.

6. SKIRROW, C., CROSS, J.H., CORMACK F. et al (2011) Long-term intellectual outcome after temporal lobe
surgery in childhood. Neurology 12, 1330-1337.

7. CROSS, J.H., JAYAKAR, P., NORDLI, D. et al (2006), Proposed criteria for referral and evaluation of children
with epilepsy for surgery Epilepsia 47, 952-959.