Here we will discuss the transient focal events. (Please see the list below). In other sections we have dealt with persistent focal neurological deficits and transient loss of consciousness.
As with other transient or paroxysmal events it is important to gather details about what happened prior to the event, during the event and after the event. Additionally, elucidate the frequency and the duration of events from the patient.
The physical examination is still relevant in patients with transient focal events. This is tailored to determine whether the nervous system is intact and that the event has definitely resolved. It is not uncommon to find focal features that persist that may indicate that the event was not transient, and may also be a clue to the etiology. This is particularly common with non-dominant hemisphere events as residual symptoms may be masked by anosognosia. Additionally, partial visual field defects such as quadrantinopsia may be missed on history alone.
Also try to determine any associated features. Were the events accompanied by a headache either before or after the event. Could the focal deficit preceding a headache be a migraine aura? or could the deficit that follows a headache be a feature of complicated migraine or basilar migraine? Think about whether the event was a gain-of-function such as limb jerking which can occur with seizures. Or whether it was a loss of function such as with transient ischemic attacks (TIA). Although it is important to note other features since loss-of-function can occur in the post-ictal phase of a seizure. This is called Todd’s paralysis. Rarely, patients with high-grade internal carotid artery stenosis can have limb-shaking TIA that may resemble a partial seizure.
Transient ischemic attacks represent dysfunction of the central nervous system due to temporary interruption of blood flow to that region. They are typically, non-stereotyped events. This means that if they are recurrent, each episode is typically different from the one before. The exception is with intracranial stenosis the events may be somewhat stereotyped because the recurrent blood flow interruption occurs within a single region in the brain. The classic stereotyped events are seizures as each seizure resembles closely the previous event. There are some exceptions as certain epilepsy syndromes can have multiple seizure types. Of note, a partial seizure should prompt search for an underlying structural cause or lesion in the brain. Hypoglycemia, usually causes global cerebral dysfunction. However, on occasion the dysfunction can manifest as a focal lesion that responds with endogenous or treatment related correction of glucose levels. Hyperglycemia, can also cause transient focal neurological dysfunction. This may mimic a stroke or cause movement disorders such as transient chorea.
Some movement disorders are paroxysmal by nature such as myoclonus or hemiballismus. There are other rare movement disorders such as the paroxysmal dystonias that can also be transient.
Lastly transient focal neurological events may represent psychogenic events in some patients. This is a difficult diagnosis to make and is often one of exclusion. However, it is important to emphasize that transient psychogenic events are more often generalized than focal as in “pseudoseizures”, and that the diagnosis is made after thorough investigation, and when the witnessed events are consistent with non-organic features.
History points to cover with transient (paroxysmal) focal events:
- Features prior to the event
- Features during the event
- Features after the event
- Duration of the event
- Frequency of the events (if paroxysmal)