Nervous system: Neurodegenerative diseases

Neurodegenerative diseases are a group of disorders characterized by the degeneration, or loss, of neurons, which are the main cells of the nervous system.

Some of the most famous neurodegenerative diseases include Parkinson disease; Huntington disease; multiple sclerosis; and amyotrophic lateral sclerosis, formerly called Lou Gehrig’s disease.

Okay, let’s start with Parkinson disease. This is a slowly progressive disorder that primarily affects individuals over 50 years old. It is caused by the degeneration of certain neurons in the brain that produce dopamine.

Dopamine is a neurotransmitter, or a chemical used to relay messages between neurons within the brain, and normally, one of its main roles is to promote movement.

In Parkinson disease, a decrease in dopamine results in difficulty initiating or controlling movement. This is typically manifested with four main symptoms, which can be remembered with the mnemonic “TRAP.”

“T” stands for tremor, which is classically described as a resting, pill-rolling tremor because it looks like someone is rolling a pill between their thumb and index finger.

“R” stands for rigidity, which is caused by tensed up muscles that resist movement. When someone tries to flex the client’s limbs, they could move in a series of stops and jerks, which is called “cogwheel rigidity.”

If it remains rigid throughout the movement, it’s called “lead pipe rigidity.” “A” stands for akinesia, which is the absence of movement and is a severe form of the more common finding: bradykinesia, which is the slowness of movement.

This can manifest as a slow, shuffling gait or a decrease in facial expressions almost to the point where the individual’s face looks like they’re wearing a mask.

“P” stands for postural instability, which causes a stooped posture, problems with balance, and an increased frequency of falls.

If the muscles involved in speech are also affected, the client might either slur words or talk too quickly to the point that it’s hard to understand them.

Likewise, dysfunction of the muscles used for chewing or swallowing might cause difficulties with eating and drinking. They are more likely to drool, and there’s an increased risk of choking.

In fact, one of the most common complications of Parkinson disease is aspiration where food, fluid, or saliva enter the airway instead of the esophagus. These can carry harmful microbes into the lungs, leading to aspiration pneumonia.

In the later stages of the disease, nonmotor brain functions can be affected as well, leading to other common symptoms that include depression, dementia, sleep disturbances, and difficulty smelling.

Interestingly, seborrheic dermatitis, an oily skin rash that appears on the scalp, face, chest, and axilla, has also been associated with Parkinson disease.

Treatment primarily includes medications that increase brain dopamine signaling. If medications aren’t effective at controlling symptoms, then a surgical treatment called deep brain stimulation can be done.

In deep brain stimulation, an electrical lead is placed in the brain region controlling muscle movement.

In any case, clients with Parkinson disease may also need physical therapy to improve their posture, balance, and range of motion and speech therapy to limit speech and swallowing difficulties.

Okay, next is multiple sclerosis. This is an autoimmune demyelinating disease, meaning the immune system inappropriately attacks and destroys the myelin.

Myelin is the protective sheath that surrounds the axons of neurons, allowing them to quickly send electrical impulses.

So, without myelin, the communication between neurons breaks down, ultimately leading to all sorts of sensory, motor, and cognitive problems.

Now, symptoms of multiple sclerosis usually manifest when the client’s between the ages of 20 and 40.

These typically occur in bouts, meaning the symptoms will undergo remission for weeks, months, or even years before a relapse where they return.

During the remission periods, the client could have little to no symptoms. Common symptoms of multiple sclerosis include speech and swallowing difficulties as well as vision problems, like double vision, blurring in one or both eyes, involuntary rapid eye movements, or even vision loss.

The bladder and bowel function might also be disturbed, leading to constipation and urinary retention or bowel and urinary incontinence.

Motor symptoms may include muscle weakness; muscle spasms; ataxia, or loss of balance and coordination; and tremor, twitching, or jerking movements that intensify as the client moves the affected limb. In the late stages, multiple sclerosis can also lead to paralysis.

Finally, other functions of the brain can also be affected, causing poor concentration and critical thinking as well as depression and anxiety.

There is no cure for multiple sclerosis, but there are medications that can lessen the severity and frequency of the relapses.