Seizures in critically ill pediatric patients

Abstract

The nervous system contains a central nervous system (CNS) and the peripheral nervous system (PNS). CNS consist of the brain and the spinal cord which takes in afferent and sensitive information and provides efferent somatic or visceral responses along with the nerves long cords that form the peripheral nervous system (PNS) that establish the connection between the CNS and the rest of the body. The mammalian brain is a highly complex series of systems, which in humans is estimated to contain 50–100 billion neurons with over a trillion synaptic connections. Neuronal communication between these synaptic connections occurs mainly through the exocytotic neurotransmitter release. Postsynaptic cell activity is modulated by the chemical signaling molecules through several methods that depend on the character of the neurotransmitter and its receptors. The downstream effects of neurotransmission trigger a wide range of behavioral and physiological processes and its dysregulation can lead to a number of diseases and syndromes. One of these diseases is seizure and epilepsy disorders, which is a one of most common neurological disorders in pediatrics. GABA is the major inhibitory neurotransmitter in mammalian brain which act mainly on GABAA receptors that is located on postsynaptic membrane, while Glutamate is the major excitatory neurotransmitter in the CNS and acts on ionotropic and metabotropic glutamate receptors located at the presynaptic terminal and in the postsynaptic membrane at synapses in the brain and spinal cord. Seizures are due to imbalance between inhibition and excitation in a localized region, in multiple discrete areas (seizure “foci”), or throughout the whole brain. The immature brain exhibits increased excitation and diminished inhibition, and this enhanced excitability increases the propensity for seizures and epileptogenesis in infancy and early childhood compared with later life. Seizures are considered one of the most common admissions to PICU or even may occur to admitted child to PICU with other disorder. The common causes of seizures and SE in PICU include developmental delay, metabolic disorders, post traumatic, CNS infection, febrile seizures, post-surgical like craniotomy, and hydrocephalus. The seizure classification system is primarily based on clinical semiology and EEG correlation, with a major distinction made between focal and generalized seizures. Focal seizures are further subdivided into simple and complex partial seizures, with the presence or absence of impairment of consciousness distinguishing the two. Generalized seizures are divided into absence, tonic, tonic-clonic, myoclonic, or atonic seizures. Evaluation of seizure disorder in any child should include his detailed history and physical examination. EEG is the electrophysiological tool in diagnosis; neuroimaging of the brain facilitates evaluation of anatomical and functional features. Initial evalua¬tion must detect the cause of seizure to exclude potential provocation, such as fever, CNS infection, traumatic brain injury, CNS tumor, cerebrovascular disease, drug withdrawal or ingestion, or toxic/metabolic causes. The EEG is a noninvasive, painless investigation of cortical and subcortical functional activity of the brain. It is easy to be performed in ICU. Structural neuroimaging has a vital role in evaluation of the child with seizures. The role of neuroimaging is to detect if there is any structural brain lesion that may precipitate seizure disorder. CT is more available and cheaper than MRI, but unfortunately MRI has a better resolution and provides more details. Seizures exist along a spectrum of severity, from benign febrile seizures to RSE. ICU level of care is recommended for management of SE but may also be necessary after any seizure for hemodynamic monitoring and ventilatory support. Early treatment of seizures and SE decreases complications and improves outcome and response to treatment.