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Nov 2011

Limitations of NIS Database in Evaluation of Epilepsy Surgery Morbidity and Mortality

Author Affiliations

Author Affiliations: Department of Neurology, Epilepsy Center, University Hospitals Case Medical Center (Drs Kaiboriboon, Lhatoo, and Koubeissi); Department of Epidemiology and Biostatistics, Population Health and Outcomes Research Core, Clinical and Translational Science Collaborative, Case Western Reserve University (Drs Kaiboriboon and Koroukian and Mr Schiltz), Cleveland, Ohio.

Arch Neurol. 2011;68(11):1483-1484. doi:10.1001/archneurol.2011.222

McClelland et al1 analyzed the Nationwide Inpatient Sample (NIS) database from 1988 to 2003 with the aim of assessing the morbidity and mortality of anterior temporal lobectomy (ATL) in patients with intractable temporal lobe epilepsy (TLE). They concluded that ATL is safe, with low morbidity and no mortality. This is an important and timely contribution to the literature, as emphasized by the excellent accompanying editorial that details the importance of using what is often highly effective surgical intervention for otherwise refractory focal epilepsy. However, the results should perhaps have been reported as including all refractory focal epilepsies rather than just TLE and all resective epilepsy surgeries rather than just temporal lobectomies. The investigators used International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes to identify patients with TLE (ICD-9-CM codes 345.41 or 345.51) and ATL (ICD-9-CM code 01.53). These codes are not specific for either TLE or ATL. Indeed, patients with intractable focal epilepsy originating from frontal, parietal, or occipital lobes are also coded as either 345.41 or 345.51 depending on the characteristics of their seizures (complex vs simple partial seizures). Similarly, any lobectomy is coded as 01.53. McClelland et al1 listed a number of limitations but did not mention this coding limitation, which may possibly change their conclusions significantly.

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