For whatever reason, the College loves non-convulsive status epilepticus. It has come up many times as one of the differentials. Notable occurences where it was the cheif topic of an SAQ include Question 20 from the second paper of 2012.
Oh's Manual explores this this issue in Chapter 49 (pp. 549, "Disorders of consciousness") by Balasubramanian Venkatesh, and Chapter 50 (pp. 560, " Status epilepticus" by Helen I Opdam.
Additional (free to read) resources could be scraped up from the internet:
Briefly, in order to qualify for this label, one must become "altered" in one's level of consciousness, and to sustain this alteration for over 30 minutes. An EEG with epileptiform discharges is required to confirm the diagnosis. Another helpful hint is the paradoxical restoration of normal alertness following the administration of an IV benzodiazepine.
One should think carefully about non-convulsive status epilepticus in any patient in whom the decreased level of consciousness has not been explained by higher-yield investigations. Statistically speaking, one study has dicovered that among patients with undiagnosed coma, roughly 8% have the characteristic epileptiform discharges on their EEG.
Non-convulsive status epilepticus is defined as seizure activity seen on EEG without the clinical findings associated with convulsive status epilepticus.
Negative symptoms:
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Positive symptoms:
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Oh's Manual also suggests some duration criteria, suggesting that one must become "altered" in one's level of consciousness for over 30 minutes in order for this sort of epileptic activity to be called a "status" of any sort.
An EEG with epileptiform discharges is required to confirm the diagnosis. Another helpful hint is the paradoxical restoration of normal alertness following the administration of an IV benzodiazepine.
One should think carefully about non-convulsive status epilepticus in any patient in whom the decreased level of consciousness has not been explained by higher-yield investigations. Statistically speaking, one study has dicovered that among patients with undiagnosed coma, roughly 8% have the characteristic epileptiform discharges on their EEG.
Why is this diagnosis difficult to make, and so frequently missed?
A study from Belfast reported on some risk factors identified among a series of patients with NCSE.
It should be added that even though the college lists these risk factors in Question 20, in fact this is from a well-established association. From over 1800 inpatient EEGs, there were 50 episodes of NCSE identified, and from this substrate the following risk factor profile was produced
The 2012 Guidelines for Management, referred to extensively in the summary of convulsive status epilepticus, do not offer anything specific for this condition. A different article from Clinical Neurophysiology (2007) also canot add anything specific. Oh's Manual recommends valproate and levitiracetam; of these the latter seems to be gaining popularity, given its relative safety.
The 2012 Guidelines for Management etc etc contain within them a huge table (Table 4) on Page 7, which patiently lists the mortality statistics for all sorts of status epilepticus. From this table, one can isolate some NCSE-specific information:
Mortality:
Time-critical diagnosis:
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Features associated with poor outcome:
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Chapter 49 (pp. 549) Disorders of consciousness by Balasubramanian Venkatesh
Chapter 50 (pp. 560) Status epilepticus by Helen I Opdam
Fountain, Nathan B. "Status epilepticus: risk factors and complications."Epilepsia 41.s2 (2000): S23-S30.
Meierkord, Hartmut, and Martin Holtkamp. "Non-convulsive status epilepticus in adults: clinical forms and treatment." The Lancet Neurology 6.4 (2007): 329-339.
Scholtes, Frans B., Willy O. Renier, and Harry Meinardi. "Non-convulsive status epilepticus: causes, treatment, and outcome in 65 patients." Journal of Neurology, Neurosurgery & Psychiatry 61.1 (1996): 93-95.
Husain, A. M., G. J. Horn, and M. P. Jacobson. "Non-convulsive status epilepticus: usefulness of clinical features in selecting patients for urgent EEG."Journal of Neurology, Neurosurgery & Psychiatry 74.2 (2003): 189-191.
Haffey, S., A. McKernan, and K. Pang. "Non-convulsive status epilepticus: a profile of patients diagnosed within a tertiary referral centre." Journal of Neurology, Neurosurgery & Psychiatry 75.7 (2004): 1043-1044.
Jirsch, J., and L. J. Hirsch. "Nonconvulsive seizures: developing a rational approach to the diagnosis and management in the critically ill population."Clinical neurophysiology 118.8 (2007): 1660-1670.
Rupprecht, Sven, et al. "Levetiracetam as a treatment option in non-convulsive status epilepticus." Epilepsy research 73.3 (2007): 238-244.