A person in a state of TGA exhibits no other signs of impaired cognitive functioning but recalls only the last few moments of consciousness, as well as possibly a few deeply encoded facts of the individual's past, such as their childhood, family, or home perhaps.

However, a TGA episode generally lasts no more than 2 to 8 hours before the patient returns to normal with the ability to form new memories.

A person having an attack of TGA has almost no capacity to establish new memories, but generally appears otherwise mentally alert and lucid, possessing full knowledge of self-identity and identity of close family, and maintaining intact perceptual skills and a wide repertoire of complex learned behavior.

The individual simply cannot recall anything that happened outside the last few minutes, while memory for more temporally distant events may or may not be largely intact.

[2][6][7] The individual experiencing TGA retains social skills and older significant memories, almost always including knowing his or her own identity and the identity of family members, and the ability to perform various complex learned tasks including driving and other learned behavior; one individual "was able to continue putting together the alternator of his car.

[4] Though outwardly appearing to be normal, a person with TGA is disoriented in time and space, perhaps knowing neither the year nor where they reside.

Although confusion is sometimes reported, others consider this an imprecise observation,[7] but an elevated emotional state (compared to patients experiencing transient ischemic attack, or TIA) is common.

[4] In the majority of cases there are no long-term effects other than a complete lack of recall for this period of the attack and an hour or two before its onset.

The leading hypotheses are some form of epileptic event, a problem with blood circulation around, to or from the brain, or some kind of migraine-like phenomenon.

"[19] Other vascular origins remain a possibility, however, according to research of jugular vein valve insufficiency in patients with TGA.

[2] There is additional speculation that atypical cases of TEA in the form of nonconvulsive status epilepticus may present with duration similar to TGA.

[28] A differential diagnosis should include:[29] If the event lasts less than one hour, transient epileptic amnesia (TEA) might be implicated.

Seeing a once competent and healthy partner, sibling or parent become incapable of remembering what was said only a minute ago is very distressing, and hence it is often the relatives who will require reassurance.

In addition to such probable TEA cases, some people experiencing amnestic events diverging from the diagnostic criteria articulated above may have a less benign prognosis than those with "pure" TGA.

MRI scans of the brain in one study showed that among people who had experienced TGA, all had cavities in the hippocampus, and these cavities were far more numerous, larger, and more suggestive of pathological damage than in either healthy controls or a large control group of people with tumor or stroke.

[13] Verbal and cognitive impairments have been observed days after TGA attacks, of such severity that the researchers estimated the effects would be unlikely to resolve within a short time frame.

[14] A large neurocognitive study of patients more than a year after their attack has shown persistent effects consistent with amnestic mild cognitive impairment (MCI-a) in a third of the people who had experienced TGA.