Differential Diagnosis
The patient's presentation of single episodes with loss of consciousness (LOC) without postictal signs, along with a history of photosensitivity, suggests a range of potential diagnoses. The following categories outline the differential diagnosis:
Single Most Likely Diagnosis
- Syncope: Given the presyncopal episode in February and the lack of postictal signs, syncope is a strong consideration. The unremarkable laboratory results, including ECG, CT head, troponin, CBC, and CMP, further support this diagnosis, as they help rule out cardiac, structural, and metabolic causes.
Other Likely Diagnoses
- Seizure Disorder: Although the episodes lack postictal signs, the history of photosensitivity could suggest a seizure disorder, particularly photosensitive epilepsy. The absence of postictal signs does not entirely rule out seizures, as some seizure types may not present with typical postictal confusion or lethargy.
- Vasovagal Syncope: This is a common cause of syncope, often triggered by specific stimuli. The patient's presentation could be consistent with vasovagal syncope, especially if there were precipitating factors such as stress, pain, or prolonged standing.
- Orthostatic Hypotension: This condition, characterized by a significant drop in blood pressure upon standing, could lead to episodes of LOC without postictal signs. It is more common in older adults or those with certain medical conditions but should be considered in the differential.
Do Not Miss Diagnoses
- Cardiac Arrhythmias: Although the ECG was unremarkable, cardiac arrhythmias such as long QT syndrome or other channelopathies could cause LOC and might not always be evident on a single ECG. These conditions are critical to diagnose due to their potential for fatal outcomes.
- Subarachnoid Hemorrhage: Despite the normal CT head, a subarachnoid hemorrhage could potentially present with LOC and normal initial imaging, especially if the bleed is small. This diagnosis is crucial to consider due to its high morbidity and mortality.
- Pulmonary Embolism: This condition can cause syncope and would be a critical diagnosis not to miss due to its potential for severe outcomes. However, the presentation would typically include other symptoms such as chest pain or shortness of breath.
Rare Diagnoses
- Mitochondrial Myopathies: Certain mitochondrial disorders can present with episodes of LOC, among other symptoms. These conditions are rare and would require specific diagnostic testing for confirmation.
- Adrenal Insufficiency: Although rare, adrenal insufficiency can cause episodes of syncope due to hypotension. This diagnosis would be considered if other signs of adrenal insufficiency were present, such as hypotension, hyponatremia, or hyperkalemia.
- MELAS Syndrome: A rare mitochondrial disorder that can cause episodes of LOC among other neurological symptoms. It is characterized by mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes.