A Review of Neurological Disorders for the Physician Assistant Exam
You will need to know about many neurologic disorders for the Physician Assistant Exam (PANCE). Among them are disorders like myasthenia gravis, multiple sclerosis, Guillain-Barré syndrome, and Tourette’s syndrome.
Picture a scenario in which a person says he or she becomes weaker as the day wears on. The person feels better when sitting down and resting, but the symptoms return after the next period of activity. The person may notice worsening vision problems, including double vision as well as drooping of the eyelids.
Myasthenia gravis is an autoimmune condition in which the most profound clinical symptom is muscular weakness. Acetylcholine is an important neurotransmitter, especially for motor function. Antibodies are formed against the postsynaptic receptor that acetylcholine binds to.
Here are the key clinical points about myasthenia gravis:
The main presenting symptoms grow worse as the day goes on. The eyes are the main organs affected, but many other skeletal muscles can be affected as well. The person may have problems with talking, chewing, and breathing.
You can order a blood test to look for antibodies to the acetylcholine receptor. It’s diagnostic in many cases. You still need further testing.
The gold standard test for establishing a diagnosis of myasthenia gravis is the Tensilon test. Tensilon is a brand name for edrophonium chloride, which works to prevent the breakdown of acetylcholine at the neuromuscular junction. If the person has myasthenia gravis, edrophonium chloride causes him or her to get better for a little while because there’s more acetylcholine around.
Note that additional studies are used in the diagnosis of myasthenia gravis, including electromyography (EMG) testing.
Because myasthenia gravis is an autoimmune condition, it’s associated with other autoimmune conditions, including rheumatologic conditions and diabetes mellitus.
If a thymoma is present, its removal is recommended.
How to treat Guillain-Barré syndrome
Guillain-Barré is a syndrome you must spot quickly. Otherwise, the affected person can die of respiratory failure. The most common presentation of Guillain-Barré syndrome is an ascending neuropathy, starting at the lower extremities and spreading upward.
The first symptoms of Guillain-Barré can be weakness or paresthesias in the lower extremities. The acute respiratory failure part comes in when the neuropathy affects the lungs. Respiratory failure is due to respiratory muscle paralysis. The person needs to be intubated.
Here are three key points about Guillain-Barré syndrome:
The trigger is thought to have an infectious etiology, such as an upper respiratory infection or gastroenteritis.
The time course of Guillain-Barré can vary from a few hours to several days.
The treatment is supportive and may also include plasmapheresis or intravenous immunoglobulin.
Multiple sclerosis is a demyelinating disorder characterized by a problem in nerve signaling. Multiple sclerosis involves significant damage to the myelin sheath. Nerves in the brain and the spinal cord don’t communicate well. Multiple sclerosis is thought to be autoimmune in nature.
You’re dealing with many different neurologic areas. Symptoms can include weakness in the extremities, paresthesias, and/or problems with ambulation. Because multiple sclerosis affects the upper motor neurons, it can cause muscle spasticity. For the PANCE, consider one of the most common presenting symptoms to be optic neuritis, which can present with eye pain, diplopia, and/or vision loss.
Concerning the eye, multiple sclerosis affects the medial longitudinal fasciculus. This structure connects cranial nerves III, IV, and VI. With multiple sclerosis, you see a Marcus Gunn pupil, which roughly equates to less constriction during a swinging flashlight test.
Here are some key points about multiple sclerosis:
Women are affected more than men, and the median age is in the 30s.
Multiple sclerosis has four subtypes, the most common of which is the relapsing-remitting subtype.
The diagnosis can be confirmed through an MRI of the brain with gadolinium, showing enhancement in the periventricular white matter.
If a lumbar puncture is done in addition to an MRI, you can test the cerebrospinal fluid for the presence of IgG oligoclonal bands.
During an acute multiple sclerosis flare, steroids are commonly used to decrease the severity of the symptoms and to calm the inflammation. Chronically, interferon has been used, although it’s not without side effects, including flu-like symptoms and depression. Monoclonal antibodies have also been used in treating common multiple sclerosis.
Tourette’s syndrome is a genetic condition characterized by tic-like movements and/or utterances. The affected person doesn’t have control over these movements. Many times, they occur in the facial area and manifest as uncontrolled blinking and constant word repetition. People associate Tourette’s with yelling curse words, but that form of Tourette’s doesn’t occur a lot.
Here are three key points concerning Tourette’s syndrome:
The diagnosis is a clinical one, usually based on symptoms and strong family history.
Tourette’s often doesn’t occur alone. It can be accompanied by disorders such as attention deficit disorder and obsessive compulsive disorder.
The treatment often involves medication, including the antipsychotics and some antidepressants. Another treatment is pimozide (Orap), a dopamine-receptor blocker.
The concussion is a form of brain trauma. With a concussion, the brain moves quickly in a way it’s not supposed to.
You hear about coup and contrecoup mediated brain injury. The coup refers to the part of the brain that’s directly affected by the brain trauma; the contrecoup refers to the opposite part of the brain that’s affected after a trauma.
Initially, the person with the concussion may lose consciousness. Symptoms of a concussion can include headache, visual problems, photosensitivity, and/or balance problems. The affected person can also be lethargic and slow to respond to commands or questions.
Repeated concussions can have long-term ramifications, including dementia and neurological damage. After an acute concussion, a person may still be affected weeks or even months later: In post-concussive syndrome, the person can be emotionally labile, have intermittent headaches, and/or have difficulty concentrating for any length of time. He or she may also complain of lightheadedness. These symptoms usually resolve with time and rest.