Neurological Disorders: Transient Global Amnesia

Introduction

Transient Global Amnesia (TGA) is a neurological disorder characterized by a brief/temporary episode of memory loss with full or nearly full resolution of the symptoms, generally without any future recurrences and consequences.

What causes TGA?

What exactly causes TGA is still not known. There could be precipitating factors like excessive stress, physical exertion etc but can occur without any such factors.

Clinical Manifestations

The episode lasts for few hours in typical cases. Before and after the episode patients are fine. The episode starts somewhat abruptly and patient usually feels something is wrong. They may repeat the same sentence again & again. They may look anxious because of sudden change in their cognitive abilities. Other than recent memory loss they do not appear to be disoriented or confused, in the sense they do most of the things coherently & appropriately. They know their name, identity, can easily recognize close family members and friends, follow other’s commands etc. It is just the isolated memory loss for recent events, and inability to form new memories (anterograde amnesia) during the episode typifies this condition.

By definition TGA is considered only when certain other similar conditions are ruled out and such conditions include;

• Stroke or mini stroke (TIA) – so patient should not have focal limb weakness, numbness, loss of sensation etc

• Seizures – so there should not be any convulsions, loss of consciousness, automatism etc. Also if any confusion/disorientation is there it should be appropriate with the short term memory loss, and not more than that

• Acute confusional states – due to seizure, stroke, mini stroke, head injuries or any other underlying electrolyte, metabolic, endocrine, drug, toxin, infections etc

Diagnosis

The TGA diagnosis is made both by its characteristic clinical presentation and by ruling out conditions mimic this disorder.

Although the opinion varies with regard to how much investigations are necessary while dealing with TGAs generally the clinicians accomplish the following investigations;

• Stroke/mini stroke work up including carotid ultrasound, EKG/ECG, holter monitor, Echocrdiogram, cholesterol etc

• Seizure work up – EEG

• Work up for any structural brain pathology –MRI scan of brain (CT of brain sometimes)

• Electrolytes, blood counts, urine analysis, chest x ray etc

Please see that not all patients may require all these investigations, so the decision is made on case to case basis.

Treatment

TGA has no specific treatment. If a patient is seen during the episode patient and their family members are reassured and made relaxed as much as possible. They are told that TGA is a benign condition without any sequelae. Also in majority of the patients it doesn’t recur again.

A neurologist is frequently involved in the care of TGA (transient global amnesia) patients.



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