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Year : 2019  |  Volume : 67  |  Issue : 4  |  Page : 1054--1055

Remaining Alert to Sedation by Antiepileptic Drugs Just after Epilepsy Surgery

Parampreet S Kharbanda, Jitupam Baishya 
 Department of Neurology, Postgraduate Institute of Medical Education and Research, Chandigarh, India

Correspondence Address:
Dr. Parampreet S Kharbanda
Department of Neurology, Postgraduate Institute of Medical Education and Research, Sector 12, Chandigarh - 160 012
India




How to cite this article:
Kharbanda PS, Baishya J. Remaining Alert to Sedation by Antiepileptic Drugs Just after Epilepsy Surgery.Neurol India 2019;67:1054-1055


How to cite this URL:
Kharbanda PS, Baishya J. Remaining Alert to Sedation by Antiepileptic Drugs Just after Epilepsy Surgery. Neurol India [serial online] 2019 [cited 2019 Oct 21 ];67:1054-1055
Available from: http://www.neurologyindia.com/text.asp?2019/67/4/1054/266285


Full Text



Antiepileptic drug (AED) optimization plays an important role in favorable surgical outcome of epilepsy surgery. Usually, AEDs are not altered for 1 year in adult and 6 months in children after surgery. Immediate postop AED modification is usually avoided. Acute postoperative seizure is an indicator of poor outcome of epilepsy surgery which occurs in approximately 4% in different studies. This might be a cause of not attempting AED tapering immediately after surgery.[1] Occasionally, AEDs have to be modified perioperatively due to inadequate seizure control or metabolic derangements. However, immediate AED alteration after surgery and its implication in seizure control is not studied to a large extent. In the present study[2], the authors deal with a unique situation for postop AED dose modification, that is, increased drowsiness after epilepsy surgery. There is hardly any previous literature available on this. They noticed that the need to reduce AEDs, especially clobazam, arose much more commonly in patients who underwent hemispherotomy, compared with anterior temporal lobectomy (ATL). They have put forward interesting hypotheses to explain this effect.

The first one is loss of cortical drive from the removal of one hemisphere. This seems like a plausible explanation, especially with large amount of brain parenchyma either removed or disconnected during hemispherotomy. It would be interesting to compare this with the data regarding drowsiness occurring after other brain surgeries involving removal of large parts of the brain.

The second hypothesis, GABA receptor denervation hypersensitivity, has been elucidated in previous studies, as referred to in the article.[3] This could explain part of the sedation.

The third hypothesis is that drugs acting only on the remaining hemisphere may cause increased drowsiness. This one seems less contributory to us, because with drug levels remaining static, the reason for the healthy hemisphere becoming more affected could be debated.

None of the patients in the present study had immediate seizures due to postop drug alterations. According to Dash et al.,[4] drug refractory epilepsy patients are on multiple AEDs which may not be required for adequate seizure control and AEDs can be reduced without increase in seizure frequency. Whether similar type of phenomenon was a reason behind nonrecurrence of seizure even after immediate postop AED reduction needs to be given a thought.

Cognitive outcome of ATL depends on side of lesion and histology, and the outcome measures vary among different domains. There may be improvement in one domain and worsening in the other. However, significant improvement in IQ in long-term follow-up has been demonstrated in children after ATL.[5] Similarly, in hemispherectomy too, cognitive outcome depends on the side of abnormality and etiology – Rasmussen's encephalitis, vascular insult, or dysplasia. Better IQ in these patients is seen in patients with Rasmussen's encephalitis and worst with patients with dysplasia. No significant change in IQ was noted post hemispherectomy regardless of the etiology.[6] As in this study, 1-year follow-up is too early to comment on cognitive outcome. Another thing to look at would be whether the level of drowsiness after hemispherotomy had any relationship with the side of surgery.

A multicenter study about practice trend of AED in immediate postoperative period may be useful to strengthen the findings of this study.

References

1Di Gennaro G, Casciato S, Quarato P, Mascia A, D'Aniello A, Grammaldo L, et al. Acute postoperative seizures and long-term seizure outcome after surgery for hippocampal sclerosis. Seizure 2015;24:59-62.
2Bajaj J, Chandra SP, Ramanujam B, Girishan S, Doddamani R, Tripathi M. Need of Immediate Drug Reduction after Epilepsy Surgery - A Prospective Observational Study. Neurol India 2019;67:1050-3.
3Waddington JL, Cross AJ. Denervation supersensitivity in the striatonigral GABA pathway. Nature 1978;276:618-20.
4Dash D, Aggarwal V, Joshi R, Padma M, Tripathi M. Effect of reduction of antiepileptic drugs in patients with drug-refractory epilepsy. Seizure 2015;27:25-9.
5Skirrow C, Cross J, Cormack F, Harkness W, Vargha-Khadem F, Baldeweg T. Long-term intellectual outcome after temporal lobe surgery in childhood. Neurology 2011;76:1330-7.
6Pulsifer M, Brandt J, Salorio C, Vining E, Carson B, Freeman J. The cognitive outcome of hemispherectomy in 71 children. Epilepsia 2004;45:243-54.