Presentation and course
Temporal lobe epilepsy is typically divided into mesial and neocortical (24). A distinct electroclinical constellation associated with a specific cause is rare for neocortical temporal lobe epilepsy but has been described for patients with autosomal dominant temporal lobe epilepsy presenting with focal seizures with prominent ictal auditory phenomena, normal MRI (42), and usually a good response to antiseizure medications (50). However, most neocortical temporal lobe seizures are characterized by their etiologic, semiologic, and electroclinical heterogeneity (39).
Neocortical temporal lobe seizure semiology varies considerably according to the area of the temporal lobe involved (24). The classical lateral temporal seizures are characterized by auditory, somatosensory, aphasia, or psychic auras followed by staring and contralateral facial and arm clonic movements, sometimes with secondary generalization. These “pure” temporal lateral seizures have an epileptogenic zone in the mid-posterior aspect of the superior temporal gyrus, usually involving primary or associative sensory areas for auditory, visual, or language functions (02). This region has few direct limbic connections, which may explain the fact that these auras may be prolonged with fewer automatisms as compared to seizures originating in other areas of the temporal lobe (30). By contrast, the lateral anterior and lateral inferior neocortical structures are highly interconnected with limbic structures (30; 02), explaining that seizures from these areas have semiology often very similar to mesial temporal seizures associated with hippocampal sclerosis (11).
The temporal pole is highly connected with the amygdala, the hippocampus, the parahippocampal gyrus, the cingulate gyrus, the orbitofrontal cortex, and the insula (14). The temporal pole cortex extends topographically to the insula (ventrally) and the entorhinal cortex (medial-inferiorly). A network analysis study revealed that the cortex extending from the temporal pole to the entorhinal area is one of the regions with the most association connections with other parts of the brain (08). Therefore, temporopolar seizures may present with different types of auras, often similar to mesial temporal seizures, including autonomic and rising epigastric sensations. In addition, tonic or clonic seizures, as well as hypermotor seizures, which are uncommon in temporal lobe epilepsy, may occur in patients with temporopolar seizures (14).
Mesial temporal lobe seizures have been studied more extensively than any other type of seizure and constitute a major manifestation of a recognized syndrome (19; 13). Because of these observations, mesial temporal lobe seizures can be used as a benchmark or gold standard against which other seizures can be compared.
Typical mesial temporal lobe seizures begin with an aura of a rising epigastric sensation and progress to altered consciousness with variable oro-alimentary (lip-smacking, chewing) and manual automatisms (picking, fumbling) (19). Manual automatisms often occur ipsilateral to the side of seizure origin, and dystonia of the hand may occur contralateral of the side of seizure origin (66). The patient may be partially responsive during a seizure and often has postictal confusion or aphasia.
Several reviews of temporal lobe epilepsy did not attempt to differentiate mesial from lateral temporal lobe seizures, implying there is no difference in clinical manifestations (02; 64). This implication is in agreement with another review that specifically examined this issue and concluded the two seizure types could not be distinguished (09). Extensive reciprocal connections between mesial and neocortical temporal structures could explain the similar clinical features from both regions (31; 07). Experiential and hallucinatory phenomena may require seizures to involve both mesial and neocortical structures (31; 07).
Nevertheless, some clinical features might help identify neocortical temporal lobe seizures.
Initial symptoms. Although mesial and neocortical temporal lobe seizures undeniably share common auras, several symptoms are more typical of seizure onset from the temporal neocortex.
Auditory hallucinations or distortions. Auditory hallucinations of any type should suggest seizure origin in the superior region of the posterior superior temporal gyrus, or at least in the lateral temporal neocortex. In a large, well-documented series of mesial temporal lobe seizures, there were no examples of auditory auras of any kind (25). On the other hand, a later report from that same group described auditory auras from both regions of seizure onset (56). A study using PET associated auditory auras with lateral neocortical onset (68). Simple auditory auras are thought to originate in the Heschl gyrus, the primary auditory area (46).
Vertiginous sensations. Vertigo has been associated with epilepsy since ancient times, but it almost certainly was over-interpreted (60; 05). True vertigo (tornado seizures) as a seizure symptom does occur, but only rarely (26). Over the years, this symptom has been equated with seizure origin in the posterior temporal neocortex or the temporoparietal junction (65); others have reported it with frontal seizure onset (41). There are, overall, few well-documented examples.
Complex visual hallucinations. Elementary visual hallucinations are a well-established symptom of seizures beginning in the occipital region, but the origin of complex visual hallucinations or visual flashbacks are generally thought to originate in the visual association cortex at the occipitotemporal or temporoparietal junctions, often including the posterior fusiform gyrus (31; 58; 07; 47). Therefore, auras of complex visual hallucinations should be equated with neocortical seizure activity unless there is strong evidence to the contrary. Overall, these complex visual epileptic auras are rare.
The typical epigastric aura with a rising sensation in the abdominal area is rare in patients with neocortical temporal lobe seizure onset and should suggest mesial temporal seizure origin (33; 48). By contrast, auditory auras can occur rarely in seizures originating in the mesial temporal region (44).
Signs (objective seizure manifestations). There are many similarities between the objective manifestations of mesial and neocortical temporal lobe seizures, but there may be some trends that help separate them. Several studies have noted that the motor manifestations (automatisms) are less common in lateral neocortical seizures (29; 23; 56). A study found that lateralized motor features (contralateral dystonic posturing, ipsilateral automatisms) seen in mesial temporal lobe seizures occurred with opposite laterality in neocortical temporal seizures (ipsilateral dystonic postures and contralateral automatisms) (16). Neocortical temporal lobe seizures generally lacked the motor activity associated with mesial temporal lobe seizures (52). One study compared patients with mesial temporal lobe epilepsy and hippocampal sclerosis with patients with neocortical temporal lobe epilepsy successfully treated by neocortical resections sparing the hippocampus. Epigastric rising sensation (6% vs. 40%), oral automatisms (29% vs. 80%), gestural automatisms (47% vs. 80%), and dystonic posturing (0% vs. 40%) were significantly less frequent in neocortical temporal lobe epilepsy (48).
Prognosis and complications
Prognosis depends on the etiology, eg, slow-growing neoplasms; vascular malformations carry their own prognostic and complication factors. The overall prognosis of neocortical temporal lobe seizures without detectable lesions has not been established.