Amnesia Flashcards
Transient Global Amnesia (TGA)
Overview
presents with transient loss of memory function
patients may appear anxious and repeatedly ask the same question
patients have no recall of events after the attack
aetiology is unknown, thought to be due to transient ischaemia to the thalamus (in particular the amygdala and hippocampus)
TGA is probably due to a transient malfunctioning of the limbo-hippocampal system which is involved in the formation of new memories and retrieval of recent memories. It normally presents in the 5th decade of life in those with pre-existing vascular risk factors, meaning there is probably a cerebro-vascular component but the cause is not known. TGA resolves spontaneously without need for treatment except for re-assurance and subsequent control of vascular risk factors.
TGA - Example Question
A 58 year old man presents to Accident and Emergency with his wife complaining of memory loss. His first noticed a problem when he had difficulty making breakfast in the morning. When you question him, he has no memory of the events of today and patchy memory of the events of the past week although his wife informs you that he had no problem with his memory yesterday. He appears extremely anxious about his memory loss and repeatedly asks you ‘Have I got dementia?’. He is able to remember his name and date of birth and recognise and name his wife. However, when using the toilet, he becomes lost and is unable to find his way back to the cubicle.
On examination his HS 1 + 2 + 0, he has corneal arcus, chest is clear. There is reduced power 4/5 to all arm movements in the right arm with normal reflexes, tone and sensation. His wife tells you that this has been present for several years following a stroke. There is no facial droop, there is no dysarthric speech or any other peripheral focal neurology and there are no cerebellar signs. Gait is normal.
He is able to count back from 20-1 and can name objects you present to him without difficulty. However he scores 0/3 on the delayed recall section of the MMSE. He is alert and fully responsive throughout the consultation.
Past medical history is of previous left sided middle cerebral territory infarct and one previous TIA one year ago. Hypercholesteroalemia, hypertension. He has a 20 pack year history of smoking and used to drink 4-6 units of alcohol per day for 20 years but stopped this 25 years ago and his wife corroborates this information. His medications include Clopidogrel, Atorvastatin, Ramipril and Bendroflumethiazide.
CT Brain was performed 3 hours after waking up and is consistent with an old left sided infarct. No other abnormality detected.
What is the most appropriate treatment for this diagnosis?
Intravenous thiamine and Vitamin B Oral thiamine and vitamin B Thrombolysis Donepezil > Supportive care only
The answer is E. This man has a diagnosis of transient global amnesia. TGA is characterised by a sudden onset of global loss of recent memory and impaired new learning with no other cognitive defects. These patients are often very aware of their memory loss making them extremely anxious. Because of the dense anterograde amnesia, it is also characterised by repetitive questioning. This is sometimes called the broken record syndrome Loss of personal identity effectively rules out TGA Patients are alert and responsive during the episode
Options A and B are inappropriate because the diagnosis is not Wernicke-Korsakoff syndrome. The presentation is too acute and too long after his heavy drinking of alcohol to be a likely diagnosis. Although there is similar defects in memory, there are normally defects in attention, concentration, frontal lobe functioning and is accompanied by symptoms such as apathy and withdrawal.
Option C is inappropriate as thrombolysis is not a treatment for TGA. In addition, thrombolysis would not usually be given to someone who has woken up with symptoms suggestive of a a stroke, even if the time window is less than 4.5 hours.
Option D is inappropriate as the diagnosis is not dementia. The onset of symptoms are too acute for this diagnosis to be considered.
TGA - Example Question
A 60 yr old woman went swimming with her family, and after finishing her swim and having a shower, her daughter noted that she became confused suddenly, repetitively asking if they had gone for a swim today. She could not remember events that occurred in the past 24 hours, and when told the answers to her questions, would ask the same question 5 minutes later. There was no change in her personality, no change in her speech, nor any muscle weakness. She is able to recall her address, the names of her daughters and husband, and her date of birth.
Her daughter said her mother did not suffer any trauma during the swim, and did not lose consciousness anytime throughout the day. The patient’s past medical history includes hypertension and depression, and she takes ramipril 2.5mg once daily, and citalopram 20mg once daily.
On examination the patient was alert, but constantly asked where she was and why was she in hospital. She was afebrile, heart rate 80 bpm, blood pressure 138/68 mmHg, respiratory rate of 18 breaths per minute, and oxygen saturation of 99% on air. Neurological examination was unremarkable, but her abbreviated mental test score was 6/10.
Her investigation results were as follow:
C Reactive protein 4 mg/l Haemoglobin 14.8 g/dl White cell count 5.6 x 10^9/L Na+ 142 mmol/l K+ 4.3 mmol/l Urea 4.2 mmol/l Creatinine 68 µmol/l Corrected calcium 2.32 mmol/l Plasma glucose 5.8 mmol/l
Computer Tomography (CT) head scan No acute intracranial pathology.
Over the next 12 hours, her memory improves and she is discharged from the observation ward.
What is the best advice for the patient with regards to driving in the future?
She can drive 4 weeks after the event if the cause has been identified and treated > DVLA need not be notified, no driving restrictions She must be symptom free for 1 year before being eligible to drive DVLA must be informed, and her licence will be revoked for 6 months She must cease driving until there is satisfactory control of her symptoms
This lady has suffered an episode of transient global amnesia, a neurological condition characterised by acute short term memory loss, lasting no more than 24 hours. Patients often developed perseveration, with repetitive questioning as they are unable to keep short term memory, but are able to recall long term memories. The aetiology of this condition is unknown.
DVLA guidelines for transient global amnesia are that as long as epilepsy, any sequelae from head injury and other causes of altered awareness have been excluded, there are no restrictions on driving and the DVLA need not be informed.
