What is the vestibular system and how is it affected by quinoline toxicity?
For those whose lives have been impacted by chronic quinoline encephalopathy, some of the symptoms they have are the result of a disturbance in their vestibular systems. It is these symptoms that distinguish it from PTSD, which people with quinism are usually diagnosed with.
The Vestibular System
What is it?
The vestibular system is a sensory system that is responsible for providing our brain with information about motion, head position, and spatial orientation; it also is involved with motor functions that allow us to keep our balance, stabilize our head and body during movement, and maintain posture. Thus, the vestibular system is essential for normal movement and equilibrium.https://neuroscientificallychallenged.com/blog/know-your-brain-vestibular-system
The vestibular system is comprised of several structures and tracts, but the main components of the system are found in the inner ear in a system of interconnected compartments called the vestibular labyrinth. The vestibular labyrinth is made up of the semicircular canals and the otolith organs (all discussed below), and contains receptors for vestibular sensations. These receptors send vestibular information via the vestibulocochlear nerve to the cerebellum and to nuclei in the brainstem called the vestibular nuclei. The vestibular nuclei then pass the information on to a variety of targets, ranging from the muscles of the eye to the cerebral cortex.https://neuroscientificallychallenged.com/blog/know-your-brain-vestibular-system
Mefloquine toxicity does irreparable damage to the brainstem. The problem here originates due to the damage to the vestibular nuclei within the brainstem. The signals are being picked up and sent by the structures of the inner ear, but the message isn’t making it to where it needs to get to in the brain because of the damaged nuclei.
As a result, those with quinism have to deal with some very unpleasant symptoms.
Vertigo, an illusory feeling of spinning, falling, or giddiness with disorientation in space that usually results in a disturbance of equilibrium, can be a sign of labyrinthine disease originating in the middle or internal ear. Adjustment to peripheral vestibular damage is rapid (within a few days). Even though a labyrinth is not intact or functioning, balance is still remarkably good when vision is present: Visual information can even compensate for the loss of both labyrinths. Vertigo can also result from tumors or other lesions of the vestibular system (eg, Ménière’s disease, or paroxysmal labyrinthine vertigo) or from reflex phenomena (eg, seasickness).https://doctorlib.info/anatomy/clinical-neuroanatomy-28/17.html
Nystagmus is an involuntary back-and-forth, up-and-down, or rotating movement of the eyeballs, with a slow pull and a rapid return jerk. Nystagmus can be induced in normal individuals; if it occurs spontaneously. It can be a sign of a lesion. Lesions that cause nystagmus affect the complex neural mechanism that tends to keep the eyes constant in relation to their environment and is thus concerned with equilibrium.
Physiologic nystagmus can be elicited by turning the eyes far to one side or by stimulating one of the semicircular canals (usually the lateral) with cool (30°C) or warm (40°C) water injected into one external ear canal (Fig 17–6). Cool water produces nystagmus toward the opposite side; warm water produces nystagmus to the same side. (A mnemonic for this is COWS: cool, opposite, warm, same.) Peripheral vestibular nystagmus results from stimulation of the peripheral vestibular apparatus and is usually accompanied by vertigo. Fast spinning of the body, sometimes seen on the playground, is an example: If children are suddenly stopped, their eyes show nystagmus for a few seconds. Professional skaters and dancers learn not to be bothered by nystagmus and vertigo. Central nervous system nystagmus is seldom associated with vertigo; it occurs with lesions in the region of the fourth ventricle. Optokinetic (railroad or freeway) nystagmus occurs when there is continuous movement of the visual field past the eyes, as when traveling by train. Nystagmus may occur during treatment with certain drugs, for example with the anticonvulsant phenytoin. Streptomycin and other drugs may even cause degeneration of the vestibular organ and nuclei.
Vestibular ataxia, with clumsy, uncoordinated movements, may result from the same lesions that produce vertigo. Nystagmus is often present. Vestibular ataxia must be distinguished from other types: cerebellar ataxia (see Chapters 7 and 13) and sensory ataxia (caused by lesions in the proprioceptive pathways; see Chapter 5).
Interruption of the pathway between the nuclei of nerves VIII, VI, and III (the medial longitudinal fasciculus, pathway of the vestibulo-ocular reflex) may occur. This results in internuclear ophthalmoplegia, an inability to adduct the eye ipsilateral to the lesion (Fig 17–7).https://doctorlib.info/anatomy/clinical-neuroanatomy-28/17.html
These are but some of the symptoms that distinguish quinism from PTSD. PTSD is a psychological condition and is treatable. Quinism is a physical disease process and is NOT treatable.
Although quinism and PTSD are unique to each other, it is possible to have both at the same time. This is usually the case with military veterans, who are more likely to be placed in situations that will cause PTSD.
Although there are ways to manage the symptoms of quinoline toxicity, there is as yet no known cure for it.
Know the facts
Visit quinism.org for more information.