Learning Objectives
- For transient memory loss or confusion, it is important to address whether memory is the only function affected
- Consider possible causes of stroke, seizure, medication side effect and metabolic disorder
- TGA is a self-limited condition that has not been proven to be associated with any illnesses
History
GL is a 58 year old man, visiting his family at an amusement park. While he was visiting, he seemed to become disengaged, apparently not remembering what rides he had taken. His family asked him to have something to eat, but he did not improve. They asked him where he was, and what their names were, and he was not able to answer correctly. He tried to answer, but the words he used were not appropriate. His behavior was otherwise unchanged, and he seemed indifferent to his problems. After 12 hours, he gradually began to improve, and he did not realize there was any problem. He could not remember where he had been or what he had done. His behavior otherwise seemed normal. He denied having a headache, numbness, weakness or a visual disturbance.
His past medical history includes diabetes mellitus, hypertension, kidney stones, and a right knee surgery. He has a history of allergy to lisinopril. He uses the medicines hydrochlorothiazide and metformin.
His family history includes stroke in his mother at age 61 and diabetes mellitus in his older sister.
He smoked 1 pack per day for 10 years. He stopped smoking 20 years ago. He has one drink per week of alcohol. He works as a manager for the regional food bank.
At the time of his interview with you, he is able to account for his symptoms in a review of systems. A ten system review is negative.
Examination
His blood pressure is 126/81, pulse 75, temperature 97.6 F. He is an alert, obese fellow, who appears calm. The heart sounds are regular and murmurs are absent. The pupillary light reflex is normal on both sides. He has normal naming, attention, language, recall, and orientation functions. There is no evidence of apraxia. Visual fields are full. Eye movements are normal. Facial and hearing sensations are normal. Facial expression, head movement, and tongue movement are normal. He has normal strength in the arms and legs and there is no tremor. The deep tendon reflexes are decreased, but symmetric, and the toes are downgoing. He has normal sensation to pinprick and proprioception. Cerebellar function is normal. Gait is normal.
Localization and Neuroanatomy
The symptoms in this case are disorientation and memory loss. At the time of his symptoms, it is possible a Wernicke’s aphasia was present. This causes difficulty with comprehension. The auditory cortex of the left parietal lobe is often implicated in this condition. Disorientation could also be caused by bilateral cerebral or thalamus impairment. Memory function may localize to the hippocampus.
Diagnosis
This is a case of a man who temporarily loses his ability to retain or retrieve memory information. Often this symptom is called confusion, but it is more specific than that. While experiencing this symptom, patients are able to read, understand, repeat, and show other signs of language function. They may not be able to recall facts, other than those with many connections to their memory from the distant past, like their place of birth or their name. If you are unable to assess a patient with this condition, a witness’s description may be important. They may be asked, “What could they do? What could they not do?” Because differentiating amnesia from other causes is difficult, the label of episode of confusion is often applied as a working diagnosis.
An episode of confusion has a much broader differential diagnosis than a symptom specific to amnesia. Causes of confusion might be a seizure, stroke, infection, metabolic derangement, medication adverse effect, medical illness, psychological disturbance, and amnesia. When the patient recovers to normal, it is more difficult to find a cause. When the symptoms persist it is important to examine the heart function, the medication history, and metabolic screening laboratory tests. A CT scan may be used if trauma or hemorrhage is suspected. Without other signs of a neurological illness, the CT scan may be expected to be normal. Patients with signs concerning for infection may be a candidate for lumbar puncture and CSF analysis. Testing for many of these causes is most effective while the symptoms are ongoing. When the patient recovers, the concern for these causes diminishes and the testing is not as helpful.
If other causes are not determined, and the symptoms last less than 24 hours, the diagnosis of transient global amnesia (TGA) should be considered. This is a diagnosis of exclusion. Certain findings that would exclude this diagnosis are:
- Recent use of sedating medications
- Evidence suggesting a seizure disorder
- Signs of systemic infection
- Recent substantial change in blood pressure or cardiac function
- Poor ventilation (hypoxia or hypercarbia)
- Recent history of head trauma
- Neurological deficits other than memory that occurred at the same time
The cause of TGA is not known. It is not associated with cerebrovascular disease. The MRI of the brain is normal in the setting of TGA, and it is not helpful to making the diagnosis. It is rare for a person to have more than one episode of TGA. This condition is not associated with dementia or other memory disorders, and it is not a warning symptom of any known illness. Our understanding of this disorder continues to evolve. Perhaps someday we will have a better understanding of its causes and effects.
Review Questions
- Symptoms or findings that would exclude a diagnosis of TGA are:
a. attempted overdose with fluoxetine prior to onset of the symptoms
b. a seizure
c. amnesia symptoms lasting for several hours
d. A and B
3. A, B, and C - TGA is a condition that is associated with:
a. Alzheimers.
b. Lewy Body Dementia
c. recent head trauma
d. stroke
e. none of the above - The best treatment for TGA is:
a. acetylcholine esterase inhibitor, such as donepezil
b. watchful waiting, since the symptoms should resolve within 24 hours
c. benzodiazepines, to increase the conductance of GABA-a receptor channels
d. high flow oxygen by face mask
e. none of the above