If you have ever had a syncope episode (passing out, or fainting), you know how scary it can be. It is scary not only from the event itself, but sorting out the causes of syncope can be both scary and frustrating. Syncope is not an uncommon association with migraine attacks. This is most often due to a vasovagal response related to the severe pain of the migraine or dehydration from vomiting. However, many migraineurs can also have some degree of dysautonomia during an attack. Dysautonomia is a dysfunction of the autonomic nervous system, which controls blood pressure, arterial dilation or constriction, heart rate, heart rhythm, sweating, and gastric motility. This is illustrated with migraine associated symptoms such as gastroparesis, dizziness, POTS, and complaints of cold hands and feet during an attack for some.
So what is syncope? Let’s first discuss the syncope definition, which is also frequently termed syncope and collapse. Syncope is a temporary loss of consciousness typically due to a brief lack of blood flow to the brain. The most common reasons are from a drop in blood pressure upon standing (orthostatic hypotension), from a vasovagal response (a form of neurocardiogenic syncope), or from the heart not pumping enough blood to the brain from an arrythmia (heart temporarily beating too fast or too low), or a weak heart muscle (such as in congestive heart failure). Near syncope is the term for “almost” having a syncope episode. This is where you feel like you “almost pass out”, and perhaps briefly get dizzy, lightheaded, woozy, and unsteady.
Syncope is rarely ever of a true neurologic cause. However, for some reason, this is still one of the most common reasons for neurology consults in the hospital setting. Therefore, I created a simple mnemonic tool that will help you consistently remember every possible cause of syncope to check off your differential diagnosis list of possibilities. I always teach this tool to the residents and medical students who are rotating on the inpatient neurology hospital service because syncope is such a common reason for neurological consultation. However, it can be helpful across all medical specialties since syncope is such a common event across all specialties. It can also be used by patients suffering from syncope to help them gain a better understanding of syncope and syncope causes.
The mnemonic tool is CONSNOC. It’s a palindrome spelled the same forwards and backwards. It’s a nonsensical word, but remembering it will quickly bring to memory every possible differential diagnosis of syncope to run through in your mind. Let’s go through each letter:
Cardiac: Think the SA (sinoatrial) node, and then think Structural and Arrhythmia causes. Structural can be outflow obstruction or low ejection fraction in CHF (congestive heart failure). Arrhythmia can be from the heart beating too fast (tachycardia) or too slow (bradycardia).
Orthostatic: This is from low blood pressure which occurs when someone stands up from a lying or sitting position. It is often seen with dehydration or blood pressure medication doses that are too high. Orthostatic intolerance is another term for this. Since this is typically such a common cause of syncope, near syncope, and dizziness, I have listed a number of treatment suggestions to help with treatment at the bottom of this page.
Neurocardiogenic: This is your classic vasovagal response where there is a sudden decrease in heart rate followed by an abrupt drop in blood pressure leading to syncope and collapse (passing out, or fainting). The physiologic mechanism for neurocardiogenic syncope can be triggered by several things. Vasovagal syncope classically occurs with a sudden scare (sees blood, intense pain, fright, etc.). Variants of the vasovagal response also include micturition or defecation syncope (think about the old lady who passed out after standing up from using the toilet, triggered by a large parasympathetic discharge), carotid hypersensitivity (think about the old guy shaving and becomes bradycardic by inadvertent carotid massage from pressing on the neck during shaving), and cough syncope or syncope with coughing.
Seizure: This is a common reason for inpatient neurological consult even though syncopal episodes are almost never from a seizure. Look for additional symptoms such as tongue biting, incontinence, and witnesses to the event for description (preceded by staring off, posturing, tonic-clonic activity, etc.). Keep in mind, you can still have convulsions during syncope called convulsive syncope (syncope with convulsions), which are not true seizures but just a manifestation of sudden drop in blood pressure and lack of blood flow to the brain. Incontinence can also occur with syncope, so it does not confirm a seizure cause. The diagnosis of seizure is best made by the company it keeps (associated symptoms with the syncopal event).
Neuropathic: This correlates to dysautonomia, also known as autonomic neuropathy. This is neuropathy involving the small nerve fibers that control heart rate, heart rhythm, blood pressure, gastrointestinal motility, sweating, and other things. The result is often a disconnect between blood pressure and heart rate where they are not working in synchronicity together, leading to symptoms such as syncope. There are a wide variety of these disorders, but the top categories to keep in mind are from chronic/toxic autonomic neuropathy such as from diabetes, autoimmune dysautonomia (such as acetylcholine receptor (AchR) autoantibody, paraneoplastic), post-viral dysautonomia, neurodegenerative dysautonomia (such as Shy-Drager Syndrome in Parkinson’s Disease), and POTS (Postural Orthostatic Tachycardia Syndrome). These disorders are often easily diagnosed by a tilt table test, or even a good set of orthostatic vitals.
Other: Think additional possibilities such as mechanical (the patient simply tripped or lost their footing), glucose (hyperglycemia, hypoglycemia)
Cerebrovascular: Think posterior circulation and vertebrobasilar ischemia. This is the other most common reason for inpatient neurology consultation in terms of TIA (transient ischemic attack) or stroke, but again, syncope is rarely the result of this. If this is the cause, it is typically associated with other neurological symptoms, particularly of the posterior circulation. So, assess for associated brainstem symptoms such as double vision, hemiparesis or hemisensory loss, slurred speech, vertigo, dysphagia, etc. Similar to seizures, the diagnosis of posterior circulation TIA or stroke is best made by the company it keeps (associated symptoms with the syncopal event).
As mentioned above, since orthostatic intolerance (orthostasis) is such a common symptom and disorder, here are some suggestions to consider to help treat it.
Guidelines for the Treatment of Orthostatic Intolerance (OI):
- Make all postural changes from lying to sitting or sitting to standing, slowly.
- Drink to 2.0 -2.5 L of fluids per day. If you have a history of congestive heart failure (CHF), you should discuss fluid intake with your cardiologist to avoid a CHF exacerbation.
- Increase sodium (salt) in the diet to 3 – 5 g per day. If not helpful and blood pressure is stable, may try 5-7 g per day. If you have a history of high blood pressure, you should discuss these adjustments with your cardiologist or primary care physician.
- Avoid large meals which can cause low blood pressure during digestion. It is better to eat smaller meals more often than three large meals.
- Avoid alcohol. Alcohol and cause blood to pool in the legs which may worsen low blood pressure reactions when standing. This can aggravate OI.
- Perform lower extremity exercises to improve strength of the leg muscles. This will help prevent blood from a pooling in the legs when standing and walking.
- Raise the head of the bed by 6 to 10 inches. The entire bed must be at an angle. Raising only the head portion of the bed at waist level or using pillows will not be effective. Raising the head of the bed will reduce urine formation overnight and there will be more volume in the circulation in the morning.
- During bad days, drink 500 cc of water quickly. This will result in an increased blood pressure within 5 minutes of drinking the water. The effect will last up to one hour and may improve orthostatic intolerance.
- Use custom fitted elastic support stockings. These will reduce a tendency for blood to pool in the legs when standing and may improve orthostatic intolerance.
- Use physical counter maneuvers such as leg crossing, squatting, or raising and resting the leg on a chair. These maneuvers increase blood pressure and can improve orthostatic intolerance.
- Avoid temperature extremes, particularly excessive heat.
- For activity planning involving higher levels of physical activity, try to plan for:
-Before rather than after a meal
-Afternoon rather than morning
-Avoid excess heavy lifting
-Avoid during excessively hot weather
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