Case 2: Bizarre behaviour in a three-year-old child

A previously healthy three-year-old girl was brought to the emergency room because of a three-day history of abnormal behaviour. The child would wake up at night and start talking to nonexistent people. Throughout these episodes, the child would be awake and would look at her caregivers, but would not respond when spoken to. The mother reported that these episodes were repetitive, occurring throughout the night and that the child had not been getting any sleep. This bizarre behaviour occurred only at nighttime. The patient’s mother reported a history of fever three days earlier and decreased activity. The child was admitted to the hospital for further workup with a provisional diagnosis of ‘acute behavioural change’ to rule out complex partial seizure, acute disseminated encephalomyelitis or herpes simplex encephalomyelitis. Workup showed normal complete blood counts, and normal electrolyte, calcium, phosphorous and magnesium levels. Cerebrospinal fluid studies were normal, including a negative polymerase chain reaction for herpes viruses. The magnetic resonance imaging scan was also normal. A sleep electroencephalogram showed delta activity and episodic slowing.

Throughout her hospital stay, the child continued to display the same pattern of abnormal behaviour and occasional abnormal movements manifested by twitching of her arms and lip smacking.

CASE 2 DIAGNOSIS: FRONTAL LOBE SEIZURES

Six days into her hospital stay, a diagnosis of frontal lobe seizure (FLS) was entertained and the child was started on carbamazepine. Good seizure control was achieved at one-month follow-up.

FLS is one of the most complicated and least understood forms of epilepsy. It is relatively common. Approximately 20% of patients admitted to epilepsy surgery programs have FLS. Generally these seizures are brief, frequent and occur in clusters of as many as 100 per night. Seizures often last less than 1 min. There is usually a definite nocturnal preponderance and an association with sleep. FLS can present in a variety of different clinical forms:

• Bizarre motor seizures manifested by explosive behavioural automatisms consisting of very complex behaviours (hypermotor seizures). Patients may jump out of bed, run around, have bicycling movements, pound on objects, rock back and forth or thrash about the bed. These automatisms are repetitive and stereotyped. Patients may also have prominent, sometimes explosive vocalization with yelling, screaming, shouted obscenities, growling, barking and laughing. The patient is often awake but unable to control motor behaviours. FLS often end as suddenly as they begin, with little, if any, postictal period.

• Brief tonic posturing of one or more extremities lasting 15 s to 20 s.

• Simple staring episodes with variable responsiveness.

Children with FLS have been found to have a low average intelligence score (mean ± SD 84±24.3); they scored below normal on tests of fine motor coordination, perceptual motor speed, drawing a complex figure and written arithmetic. The majority of patients exhibit attention-deficit and hyperactivity or compulsivity and behavioural problems.

FLS can be cryptogenic (nonlesional) or can be caused by a variety of intracranial abnormalities involving the frontal lobes. Such abnormalities include tumours, vascular malformations, cortical dysplasia and autosomal dominant frontal lobe epilepsy. FLS can occur in all age groups depending on the underlying cause. Cryptogenic, nonlesional FLS and autosomal dominant frontal lobe epilepsy usually manifest during the teenage years, but they can begin during the first decade of life. The autosomal dominant frontal lobe epilepsy presents with typical FLS of the bizarre hyperactive type or asymmetrical tonic seizures. These seizures usually respond well to small doses of antiepileptic medications.

The importance of a thorough history cannot be overemphasized in making the diagnosis of FLS. The typical clinical characteristics discussed above can usually be recognized by an experienced physician on history alone. Interictal encephalogram (EEG) is usually normal. Long-term video EEG monitoring in children, however, has demonstrated frontal or bifrontal epileptic discharge during seizures. Magnetic resonance imaging is normal in most patients with FLS. Abnormal findings reported in a small subset of patients included focal cortical dysplasia, low-grade tumours and vascular malformation.

A psychogenic nonepileptic seizure (NES) or pseudoseizure is the most important diagnostic consideration in the differential diagnosis. Clinically, NES differs from bizarre hyperactive FLS in that they are less stereotyped and longer in duration, and are associated with waxing and waning asynchronous motor activity with variable responsiveness. NES has no underlying structural or EEG abnormality and usually occurs while awake. They are usually associated with psychiatric diseases such as post-traumatic stress disorder, conversion, factitious disorder, malingering and depression. A history of trauma, especially childhood sexual abuse, has been associated with NES. On the other hand, depression is the only psychiatric comorbidity found commonly in patients with bizarre hyperactive seizures. Parasomnias, especially night terrors, are another important differential diagnosis in children. In contrast to FLS that occurs throughout the night, parasomnias tend to occur in the first few hours of sleep.

Cryptogenic nonlesional FLS is treated with standard antiepileptic medications. Autosomal dominant frontal lobe epilepsy is generally treated with carbamazepine. Fifty per cent of children demonstrate seizure control on antiepileptic medications, with carbamazepine and valproic acid being the most effective treatments. Epilepsy surgery is usually reserved for intractable seizures. Epilepsy surgery can be performed with the help of intracranial EEG to localize the epileptogenic zone in patients with a normal magnetic resonance imaging scan, allowing for resection of that zone. Success rate for a seizure-free outcome after surgery varies from 50% to 75%. Other treatment alternatives when resection cannot be performed include vagal nerve stimulator implantation and corpus callosotomy.

CLINICAL PEARLS

• FLS of the bizarre hyperactive type can easily be mistaken for NES. The clinician should be aware of the clinical differences between the two disorders because cause and management are completely different.

• FLS can be recognized by its unique repetitive or stereotyped clinical pattern and its nocturnal preponderance. A good history is very helpful in making the diagnosis.