Leukemia (Blood Cancer)

 I'm going to be talking about vertigo and specifically trying to understand the causes of vertigo.  Vertigo is a descriptive term for a sensation that there's movement between the patient and their environment so they may describe that they're moving or that the room is moving and often this is a horizontal spinning sensation similar to the sensation you'd get when spinning on a swing and then abruptly stopping and the environment continues to feel like it's moving around you.

 

Vertigo is often associated with nausea vomiting may be a sweating sensation and generally feeling unwell so let's go through the pathophysiology of vertigo. Vertigo is caused by a mismatch between the sensory inputs that are responsible for maintaining your posture and these inputs are a vision from your eyes proprioception from your joints and signals from the vestibular system. The Vestibular System is the most important sensory system to understand when we're learning about vertigo, the vestibular apparatus is located in the inner ear it consists of three loops called the semicircular canals that are filled with a fluid called endolymph. These semicircular canals are oriented in different directions to detect different movements of the head so as the head turns the fluid shifts within the canals this shift in a fluid is detected by small hairs called stereocilia that are found in a section of the canals called the ampulla.

This sensory input of shifting fluid is transmitted to the brain by the vestibular nerve and it lets the brain know that the head is moving in a particular direction so essentially this vestibular system is important for detecting the movement of the head. The vestibular nerve carries signals from the vestibular apparatus to the vestibular nucleus in the brainstem and also to the cerebellum, the vestibular nucleus then sends signals to the oculomotor, the trochlea, and abducens nuclei which are responsible for controlling eye movements and also to the thalamus the spinal cord and the cerebellum. The cerebellum is responsible for coordinating movement throughout the body so therefore the vestibular signals help the central nervous system coordinate eye movements and movements throughout the body, vertigo can be caused by either a peripheral problem usually affecting the vestibular system or by a central problem usually affecting the brain stem or the cerebellum.

So first let's talk about vestibular problems there are a number of vestibular causes of vertigo. The three most common causes to be familiar with are benign paroxysmal positional vertigo Meniere's disease and vestibular neuritis, first let's talk about benign paroxysmal positional vertigo or BPPV this is caused by crystals of calcium carbonates which are called Auto Konya that become displaced into the semicircular canals they may be displaced by a viral infection, head trauma, aging or without any clear cause at all these crystals disrupt the normal flow through the canals and therefore disrupt the function of the system the symptoms are usually positional because movement is required to confuse the system and when the patient becomes completely still there's no disruption to that movement of fluid so their symptom free therefore the attacks of vertigo are triggered by movement and they can last around a  minute before the symptoms settle often symptoms occur over several weeks and then resolve but they can reoccur weeks or months later a special test called the whole pipe maneuver can be used to diagnose BPPV.

Next, let's talk about many diseases this is thought to be caused by an excessive buildup of endolymph in these semicircular canals causing a higher pressure than normal which disrupts the sensory signals causes acts of hearing loss tinnitus vertigo, and a sensation of fullness in the ear. These attacks typically last several hours before they settle down and it often occurs in middle-aged adults and is not associated with movement so the symptoms are not positional. Patients will have spontaneous nystagmus during the attacks where the eyes flicker backward and forwards over time the patient's hearing will gradually deteriorate between attacks.

Finally, let's talk about acute vestibular neuritis which describes inflammation of the vestibular nerve this is usually attributed to a viral infection however it can occur without any other symptoms of the viral infection. The disruption to the function of this vestibular nerve leads to a mismatch in signals to the brain causing vertigo. Usually, the history is of acute onset vertigo that lasts for several weeks before gradually resolving other peripheral causes of nystagmus and these are trauma to the vestibular nerve. Vestibular nerve tumors particularly acoustic neuromas otosclerosis hyperviscosity syndrome and herpes zoster infection often occur with facial nerve weakness and vesicles around the ear which is known as Ramsay Hunt syndrome.

Next, let's talk about central causes of vertigo pathology that affect the cerebellum or the brainstem disrupts the signals from the vestibular system, and cause vertigo the most common cause of pathology that results in a central cause of vertigo is posterior circulation infarction which is basically a stroke in this area tumors. Multiple sclerosis and vestibular migraine are all of the central causes of vertigo that will cause sustained nonpositional vertigo because they aren't caused by a disruption to the movement of fluid within the semicircular canals. They're caused by disruption to the interpretation of signals within the central nervous system itself.

Now let's talk about posterior circulation infarction these patients will have a sudden onset of vertigo that may be associated with other symptoms such as a taxi er diplopia or double vision other cranial nerve defects or limb weakness tumors in the cerebellum or the brainstem will have a gradual onset with associated symptoms of Cerebellar or brainstem dysfunction. Multiple sclerosis may cause relapsing and remitting symptoms with other features of MS such as optic neuritis or the transverse myelitis and vestibular migraine will cause symptoms that last minutes to hours often associated with visual aura and a headache.

So finally a brief summary of the causes of vertigo the top peripheral causes to remember is benign paroxysmal positional vertigo Meniere's disease and acute vestibular neuritis and the top central causes to remember are posterior circulation infarction tumors in the cerebellum or brainstem multiple sclerosis and vestibular migraine.