Back To CourseHuman Biology Study Guide
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Patricia is an experienced registered nurse who has worked in various acute care areas as well as in legal nurse consulting. She also has a BSChE.
''Dictation: This is Dr. Tim Rogers, dictating on John Doe, June 29, 2017. Mr. Doe is a pleasant, physically fit 28-year-old Caucasian male who sustained a coup contrecoup brain injury in a skydiving accident. His parachute opened too early, and he was thrown around quite a bit by the gravitational force of the sudden line snapping. He was unconscious for a brief period of time, probably less than thirty minutes. His friends called 9-1-1, and he was brought to the ER in an ambulance. He woke up in the ER and was oriented to person, place and time, but his first verbal comment was, Doc, I can't see right!''
A scotoma is a break or interruption in the visual field. The plural of the word is not scotomas, as one might think, but is scotomata. A scotoma can occur in one eye or both, in the center or at the outer edges of the visual field, and can occur alone or there can be several. It can be temporary, but in the majority of cases, it's permanent. There are many possible causes of scotoma, and it can be a very debilitating and life-altering disorder.
There are several main types of scotoma. Most are permanent, but the type that's associated with a migraine headache is temporary and is often part of the headache aura, or subtle change in perception that occurs before the migraine begins.
Let's look at a few different types. A scintillating scotoma is the type of scotoma that occurs before the onset of a migraine headache. However, it can occur on its own. This scotoma appears as a flickering, arc-shaped light that encroaches upon the central visual field.
A central scotoma is perhaps the most troublesome type, as it's a dark spot in the center of the field of vision. The remaining visual field remains normal, often causing the patient to focus on the periphery, or outer boundaries, of the field. This makes daily activities such as reading and driving very difficult.
A peripheral scotoma is a dark spot along the edges of the field of vision. While it does interfere with normal vision and all activities that depend upon that, it's not as difficult to deal with as a central scotoma.
In a hemianopic scotoma, half of the visual field is affected by the dark spot. This can occur on either side of the center, and can affect one or both eyes, but usually affects them both. This is also sometimes called homonymous hemianopsia.
A paracentral scotoma is a dark spot that occurs near, but not in, the central visual field.
Lastly, there is the bilateral scotoma, which appears in both eyes and is caused by some type of brain tumor or growth. It is relatively rare.
A scotoma is actually not a disease unto itself, but is a symptom of some other underlying disease or cause. It's important to diagnose and treat the problem that caused the scotoma to prevent it from getting worse.
Any type of disease or damage to the brain can be the cause of a scotoma. In the introductory example, the patient had a traumatic coup contrecoup brain injury. In this type of injury, the head is shaken in such a way that the brain actually slams into the skull at the point of impact, and then slams back against the opposite part of the skull. A stroke or brain tumor can also be the cause of one or more scotomata.
Disturbances in the circulatory system of the eye can also cause scotoma. Spasms of the arteries of the eye are likely to be the cause of the scintillating scotomata that often precede a migraine headache, and blockages of the retinal blood vessels can also cause a more permanent scotoma.
Inflammation of the optic nerve, or second cranial nerve that serves the eye, can cause a scotoma to form. Demyelinating diseases, or diseases in which the myelin sheath of the nerve cells is damaged, such as multiple sclerosis, can also cause scotomata, as they interfere with the function of the optic nerve.
Diseases of the eye itself, such as glaucoma and macular degeneration, can also be the cause of scotoma. Glaucoma is an eye disease caused by increased pressure in the eye, while macular degeneration is the gradual breakdown of the macula, or back portion, of the retina.
Scotoma can also occur as a result of poisoning by various toxins, such as antifreeze, wood alcohol, and quinine, which is used to treat malaria.
Let's review. A scotoma is a break or interruption in the visual field. The plural of this word is scotomata. Scotomata can be very life-altering and debilitating.
There are several different types of scotoma, but the most serious is the central scotoma, which is a dark spot in the central field of vision that is most often permanent. However, sometimes scotoma can be temporary, as in the case of scintillating scotoma, which causes a change in perception that occurs just prior to a migraine headache. Any of the types of scotomata can occur in one or both eyes.
There are many possible causes of scotoma. Any traumatic brain injury, such as the coup contrecoup injury, can be a cause, as well as brain tumors or stroke. Problems with circulation in the eye itself can also be the cause. Inflammation of the optic nerve or demyelinating diseases like multiple sclerosis can also cause scotoma. Glaucoma, macular degeneration, and ingested toxins such as wood alcohol, antifreeze, and quinine may also be causes of scotoma.
Medical Disclaimer: The information on this site is for your information only and is not a substitute for professional medical advice.
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Back To CourseHuman Biology Study Guide
19 chapters | 266 lessons