SEIZURE-LIKE DISORDERS (SEIZURE MIMICS)
Many conditions present with paroxysmal seizurelike episodes without true epileptic activity but easily confused with seizures. Anticonvulsants have no role in these cases. Some important non-seizure paroxysmal disorders are as follows:
Syncope may be defined as “transient loss of consciousness due to sudden alterations in cerebral blood flow or brain metabolismquot;, with or without seizure activity, flaccidity and autonomic disturbances.
Although very common and mostly benign, prolonged or recurrent syncope may terminate into death or significant neurological sequelae. Clinically, irrespective of the cause, most syncopal attacks are characterized by—(a) sudden onset, (b) transient dizziness or loss of sensorium for not more than 1-5 minutes, (c) spontaneous recovery in most cases, and (d) tendency for recurrence.Etiologically, syncopal attacks may be divided as:
• Simple or vasovagal syncope, more common in adolescent females, precipitated by pain, fear, heat or sudden change in posture.
• Cardiogenic syncope, due to underlying coronary artery disease, arrhythmia (long QT syndrome) or left ventricular outflow obstruction, e.g. aortic stenosis, often precipitated by exercise or stress.
• Cough syncope, e.g. in asthma, pertussis, etc. due to sudden rise in intrathoracic pressure with consequent drop in systemic venous return gt; cardiac output gt; cerebral blood flow.
• Hypoglycemic syncope, usually seen after prolonged fasting or in insulin-dependent diabetics, with profuse sweating, cloudy sensorium. It is relieved quickly after eating.
• Neuro-psychiatric syncope may be seen in migraine, anxiety disorders, hysteria or breath-holding spells. While transient EEG changes are common and clinical
presentation often mimics absence seizures, syncope is not a seizure disorder.
Diagnostic evaluation of these cases aims to distinguish rare cases of organic syncope from simple vasovagal episodes.
Tilt-table test and carotid massage are two simple and reliable tests to identify simple syncope, while selected recurrent cases need 24-hour Holter monitoring, EEG studies and behavioral assessment, to exclude other causes.Treatment depends on the cause. Although no treatment is necessary for single attacks except counseling, recurrent vaso-vagal syncope may be treated with #946;-blockers.
Paroxysmal non-epileptic events (pseudoseizures or psychogenic seizures) are common in adolescents, specially females or those with neurotic personality. Past history of true epilepsy may be present in some cases.
Pseudoseizure is primarily a diagnosis of exclusion, that should be suspected in cases with—(a) bizarre motor movements with unusual postures, (b) absence of cyanosis, tongue-bite, urine/stool incontinence during the episode, (c) ability to enact the seizure on request, (d) normal EEG after seizure. Serum prolactin levels are significantly increased after true seizures but not in pseudoseizures. Psychiatric consultation is necessary in these cases.
Behavioral disorders, e.g. breath-holding spells (Ch 4.6.1) and night terrors (Ch 4.5.) may also be confused by epilepsy.
Benign paroxysmal vertigo is mainly seen in toddlers (rare gt;3 years) with paroxsymal attacks of ataxia, nystagmus and vomiting with pale, frightened appearance. Each attack may last from few minutes to days with variable frequency and severity. Neurological examination is normal except an abnormal caloric test during attack. These children are susceptible for motion sickness and migraine in late life. Severe or frequent attacks may be treated with PO diphenhydramine (5 mg/kg/d) or Flunarizine.
Apart from seizures, these cases should also be differentiated from other causes of vertigo in childhood,
e.g. (a) acute labyrinthitis, (b) meniere syndrome, (c) motion sickness, (d) migraine, (e) cerebrovascular episodes, and (f) cerebello-pontine angle tumors.
Benign neonatal sleep myoclonus presents with a burst of myoclonic or clonic movements only during sleep in the first week of life, which is typically aborted as soon as the baby awakens.
Episodes may last for few weeks to months before disappearance and no treatment is required except reassurance.Cataplexy manifests as sudden and transient (a few seconds) loss of muscle tone with fall, precipitated by laughter, stress or frightening experience (d/d atonic seizures). Many neurostimulant and neurodepressant drugs have been used in these cases.
Narcolepsy, an uncommon paroxysmal disorder before adolescence, denotes paroxysmal attacks of irrepressible sleep attacks during day time, from which the patient is easily arousable (d/d true absence seizures). EEG reveals intermittent attacks of REM sleep. Modafinil acetamide (PO 200 mg OD) is drug of choice in confirmed cases.
Shuddering attacks are seen in 6 months-6 years age group as multiple clusters of shivering movements with intervening asymptomatic periods. Many of these cases may develop benign tremors in later age.
Drug dyskinesia, usually after antiemetics or tranquilizers, presents with sudden bizarre dystonic movements and oculogyric crisis, with normal consciousness, speech may be slurred during the attack. These movements are rarely recurrent and history of suspected drug ingestion helps in diagnosis. Although most attacks abort gradually in next 6-12 hours, Diphenhydramine hydrochloride may be used in cases with severe painful dystonia.
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