The mechanism by which patent foramen ovale (PFOs) are associated with ischemic stroke is believed to be paradoxical embolism. It has been observed that people with migraine with aura have a larger than expected concomitant prevalence of PFO compared to people without migraine. Transient global amnesia is considered to have a similar pathophysiology to migraine, and an association with PFO has also been observed. The mechanisms by which obstructive sleep apnea (OSA) increases the risk of ischemic stroke are multiple and all contribute to the ischemic event. As the risk seems associated with the multiple physiological abnormalities that accompany OSA and facilitated by a PFO, stroke prevention could potentially be achieved by improving OSA and reducing the right-to-left shunt treatment, antithrombotic therapy, PFO closure. Antithrombotic therapy should be given as well, in light of the greater overall cardiovascular risk.

Disorders of consciousness range from deep coma in a patient with a mass lesion to delirium in a hospitalized elderly patient. Neurohospitalists are often asked to determine the etiology of the patient's altered state and to provide prognostic information and treatment recommendations. This review addresses the common syndromes associated with consciousness disorders, including coma, vegetative and minimally conscious states and syncope. A comatose patient, by definition, has eyes closed with no response to voice or pain and no comprehensible speech or awareness of self and surroundings. Patients typically evolve into a chronic disorder of consciousness, often initially a vegetative state and then potentially into a minimally conscious state. Syncope is a rapid-onset and self-limited loss of consciousness which is typically accompanied by loss of postural tone. Transient global amnesia (TGA) is a clinically defined condition with abrupt onset of anterograde and variable retrograde amnesia lasting up to 24 hours.

Dementia is a syndrome, not a specific diagnosis. There are more than 70 recognized disorders that cause dementia and the ultimate responsibility of determining the precise cause of dementia lies with a multidisciplinary team or dementia clinic. Mild dementia, however, is often missed unless mental status is formally assessed. Transient global amnesia (TGA) is a rare, but dramatic entity with a benign prognosis. TGA is characterized by abrupt, temporary inability to form new memories (anterograde amnesia) and variable impairment of recent and remote memory. TGA spares nonmemory functions, such as language and visuospatial skills. The diagnostic evaluation of dementia is best done in the outpatient setting. Common complications, such as pneumonia and urinary tract infection, are considered in demented patients with a precipitous decline in cognition. Infectious precautions are required when evaluating patients with rapidly progressive dementia.

This chapter reviews and contrasts the clinical and neuropsychological features of transient global amnesia (TGA) and transient epileptic amnesia (TEA). It discusses their pathophysiology and outlines an approach to the management of patients with transient amnesia. Attacks of TGA follow a wide variety of stresses, including strenuous exertion, sexual intercourse, immersion in water, pain and emotive events. Neuropsychological testing during attacks has confirmed that amnesia is much the most striking deficit in TGA, and is often the only impairment. In principle, the patchy impairment of remote memory which affects a high proportion of patients with TEA must have one of three explanations: failure to encode episodes into long-term memory, failure to consolidate and maintain such memories or failure to retrieve memories which have been successfully stored. TGA is a common and clearly defined clinical syndrome the aetiology of which remains obscure. Patients with TEA often benefit from anti-convulsant medication.