Discussion
In this case, the patient developed unexplained postoperative DOC, which
was suspected to be an epileptic seizure based on the diagnostic and
therapeutic intervention. Epilepsy is considered one of the most serious
neurological disorders, affecting over 70 million people worldwide
[4]. Its incidence follows a bimodal distribution, with the highest
risk observed in infants and the elderly. Furthermore, it has been
pointed out that approximately 30% of elderly-onset epilepsy cases
experience status epilepticus at the time of initial onset, and among
them, the frequency of NCSE is high [5]. NCSE is defined as a
condition characterized by non-convulsive clinical neurological symptoms
caused by EEG seizure activity lasting for more than 30 minutes [6].
The symptoms of NCSE have been reported to manifest as altered
consciousness, in the form of confusion or coma, as well as language
impairment, myoclonus-like movements, anxiety, excitement, delirium and
extrapyramidal symptoms [7]. In this case, the patient initially
regained consciousness after completion of general anesthesia. However,
shortly thereafter, he experienced loss of consciousness that persisted
for more than 30 minutes. Although EEG could not be performed during the
episode of impaired consciousness, it is likely that the patient
experienced NCSE characterized by the predominant symptom of DOC. NCSE
is a condition that is often observed in patients with unexplained DOC
in whom no clear cause is identified by imaging. The diagnosis and,
hence, treatment of this condition, is often missed because it does not
present with obvious seizures. However, if treatment is delayed, it can
lead to irreversible brain damage. Therefore, early diagnosis and prompt
treatment are crucial [8]. The risk factors for the development of
NCSE include prodromal generalized tonic-clonic seizures, a history of
epilepsy, advanced age, female gender, and a history of brain injury.
Therefore, in the presence of any of these risk factors in a patient
with unexplained DOC, NCSE should be considered in the differential
diagnosis [9,10]. In this patient, there were no specific risk
factors except for advanced age, which made the diagnosis challenging.
The treatment of NCSE often involves the administration of
benzodiazepines, which have been found to be effective [11,12]. In
this case, significant improvement in consciousness was observed after
administration of diazepam. Other medications, such as phenytoin and
valproic acid, might also be considered in the treatment. Newer
antiepileptic drugs, such as levetiracetam, which have fewer side
effects and drug interactions, can also be used for the treatment of
NCSE [13].
It is indeed rare to observe the onset of NCSE immediately after the
completion of general anesthesia for surgery. To our knowledge, there
have been a few reported cases of NCSE occurring after neurosurgical
procedures, but only one reported case of NCSE following non-cranial
surgery [14]. Our experience suggests that when organic causes for
post-anesthetic impaired consciousness are ruled out, NCSE should be
considered in the differential diagnosis. If feasible, immediate EEG
monitoring should also be considered to aid in diagnosis.
In this case, although a definitive diagnosis of NCSE could not be made
due to the unavailability of immediate EEG monitoring, improvement in
consciousness level immediately following the administration of diazepam
as a diagnostic and therapeutic intervention strongly suggested the
possibility of NCSE. Post-anesthetic DOC can often be attributed to
residual effects of anesthetic drugs, making it challenging to diagnose
NCSE. However, in elderly patients, NCSE should be considered in the
differential diagnosis of DOC. Fortunately, in this case, the patient
was managed without severe neurological complications.