The Anatomy of Vertigo

The Anatomy of a Headache The Anatomy of a Pinched Nerve Let's talk about vertigo. Technically a diagnosis of vertigo should be confined to a sensation of spinning or rotation in the absence of movement. However, for purposes of this conversation we will discuss the wide range of vestibular disorders that are often described as dizziness or vertigo. When people say they are feeling dizzy it usually means that they have a feeling of being in motion without actually being in motion. It could be the feeling of swaying like a boat, feeling drunk or woozy, feeling a sense of fogginess, or even just really light headed. It's not unusual for people to feel these sensations periodically after having too much to drink or after a wild ride on a roller coaster. However, if you have these sensations chronically without a precipitating event, then you likely have chronic vestibular dysfunction. Chronic vestibular dysfunction is challenging to diagnose and treat. It can be a secondary effect of a different diseases like multiple sclerosis or it can be a primary vestibular disorder like positional vertigo. Either way, these conditions can be related to the following pieces of anatomy:

The Semicircular Canals When it comes to a true sense of vertigo where you or the world appear to be spinning, then the most likely culprit are these tiny little tubes in your inner ear called the semicircular canals. These tiny little tubes in your ears are roughly oriented into in the main directions of movement of your head. When you bend your head forward or backward, turn, or bend to the side these little tubes give powerful signals to the brain to let you know where your head is moving in space. These canals are lined with tiny hair cells called cilia which are your receptors for balance. The canals are also filled with a fluid called endolymph. When your head moves, this fluid moves inside the canals and stimulates these hair cells. These organs are almost hard wired to movement of your eyes, so that when you move your head in one direction, your eyes reflexively move the opposite way.

What Can Go Wrong? The most common problem to affect these canals is called benign paroxysmal positional vertigo (BPPV). In this condition, little tiny crystals in the otolith get dislodged and jump around in the semicircular canals. These crystals will move the hair cells in the canal causing them to fire without the appropriate head movement. When that happens, your inner ear is firing like your head is moving in one direction when it is not actually moving. This causes a sensory mismatch in which the canals almost always win. Therefore your ears tell your brain your head is moving, and your eyes will start moving inappropriately to match it, and now the world is perceived as spinning.

The Otolithic Organs The otoliths are a pair of small swellings in the inner ear called the utricle and the saccule. Like the semicircular canals, they are lined with small hair cells that become stimulated by the movement of fluid and crystals as the head moves. For ease of understanding, the utricle is a more horizontal structure and detects side to side motion of the head, while the saccule is more vertically oriented and detects up-down movements. These play a huge role in the brain's perception of gravity. As a chiropractor, this plays a huge role in what we do. One of the first signs of a problem in these little organs is the presence of head tilt. Over time, this head tilt can start causing neck pain and headache.

What Can Go Wrong? The otolithic organs are not understood as well as the semicircular canals. The crystals that cause BPPV are dislodged from the utricle and they may play a role in otolithic disorders. When the otoliths are involved, you are less likely to feel the "spinning" type of vertigo, but more likely to have a sense of tipping over, walking off balance, or feeling like you're rocking on a boat. The otoliths are also likely to be implicated in motion sickness. This can also lead to abnormal head tilts, blurry vision, neck pain, and headaches. You can read more about that here: Is Head Tilt Driving Your Brain Crazy The otoliths are susceptible to toxicity from certain medications and various enviornmental toxins. When substances affect the inner ear, it can cause ringing in the ears and balance disorders. Substances like certain antibiotics, heart medications, aspirin, diuretics, chemotherapy compounds, and more. One of the most common compounds I see that is ototoxic includes neurontin. A common drug used to treat chronic pain and neurological disorders. The otoliths can also be prone to traumatic head injury, but we'll get more into that shortly.

The Vestibulocochlear nerve The vestibulocochlear nerve is a specialized nerve called a cranial nerve. This nerve travels from your inner ear to the brain stem. This nerve is linked to specialized receptors that transmits sound and balance information from the inner ear so that your brain can process it. Whenever you your otoliths or semicircular canals sense movement, the hair cells of the inner ear fire and travel down the nerve towards the brainstem for processing.

 What Can Go Wrong? Because this nerve transmits both sound and balance information, damage to this nerve can compromise both your sense of hearing and balance. This nerve is susceptible to inner ear infections, tumors, and neurodegeneration. Illnesses that cause labyrinthitis or acoustic neuritis can make you feel dizzy and off balance through the inflammatory response.

The Brainstem The brain stem is the most primitive part of the brain responsible for most life sustaining processes in the body. It is also home to the cells that form the specialized cranial nerves like the vestibulocochlear nerve we just discussed. The brain stem also acts like a central processor of a computer. It takes a lot of the inbound information from the body and filters it down into a signal that the brain will how to use it. This is especially important for your balance system. A specific area of the brainstem called the vestibular nuclei are responsible for coordinating the signals coming from your eyes and ears. When your head moves, the inner ear sends signals to these brainstem cells which will help move the eyes. This way your head movement and eye movements are purposeful and coordinated.

What can go wrong? The brainstem can be injured by strokes and traumatic injury. Dizziness is one of the primary symptoms of stroke and concussion because of the way they hit the brainstem. That means your inner ear can be healthy or in tact and your world is spinning and off balance because the part of the brain that is supposed to make sense of all of this is injured. These patients often struggle worse with their balance symptoms because they don't play by the same rules as the previous types. The balance issues may be unrelenting or unpredictable because the central control system is compromised. A central cause of vertigo is likely the culprit in cases of migraine associated vertigo. These cases of vertigo are of central origin and usually require treatment or therapies that are a lot different from those that affect the semicircular canals, otoliths, or vestibular nerves.

The Neck The neck is a really common but under appreciated cause of vertigo. Because the neck holds our head up, it provides a lot of feedback to the brain about where the head is in space. The contraction of your neck muscles tell your brain if your head is pointing up, down, left, or right. Additionally, your spine is loaded with millions of tiny little sense organs or cells called mechanoreceptors. These receptors fire in response to the way that muscles and joints are loaded. When they fire, it helps the brain decide on the quality and accuracy of movement

What can go wrong? Injuries, misalignment, or degeneration of the the spine can alter the way these mechanoreceptors fire. If your brain is getting poor or inaccurate feedback from the neck, then it causes a sensory mismatch with the eyes and inner ears. This sensory mismatch is at the core of vertigo and balance disorders. Many of these cases respond favorably to chiropractic adjustments or other types of manual therapy. In fact, a diagnosis of cervicogenic vertigo is usually based off the fact that vertigo resolved because of a treatment to the neck. It's a challenging condition to diagnose because it's a rare condition where the treatment often dictates the diagnosis.

Don't Leave Your Doctor's Office with a diagnosis of vertigo A lot of people leave a doctor's office with dizziness and come back with a diagnosis of vertigo. This is an utterly useless diagnosis. They've basically taken the fact that you said you have dizziness, and gave it a latin name. You can read more about that here: Vertigo is NOT a Diagnosis You have to figure out what anatomy is causing your condition. While vertigo looks and feels similar no matter what anatomy is causing it, the way that it needs to be treated can vary greatly. Vertigo and balance disorders are tough conditions to treat medically because drugs do a poor job selectively targeting these very different pieces of anatomy. Many of these cases have a mechanical and neurological cause, and can be rehabilitated using mechanical and neurological strategies. If you see a doctor who is not caught up on current strategies to rehabilitate balance disorders, then you might be leaving a doctor's office thinking that your balance problem is untreatable. The first step to addressing vertigo is to identify the anatomical cause, and then getting you to the right professional who is equipped to manage this debilitating condition.