Overview

The nervous system is a complex, highly specialized network. It organizes, explains, and directs interactions between you and the world around you. The nervous system controls:

• Sight, hearing, taste, smell, and feeling (sensation).
• Movements you choose to make (voluntary) and those that happen without your thinking about them (involuntary). These include breathing and heartbeat.
• The ability to think and reason. It allows you to be awake (conscious), to have thoughts and memories, and to use language.

The nervous system is divided into two parts:

• The brain and spinal cord (central nervous system).
• The nerve cells that control how you feel pain, touch, or temperature (peripheral nervous system).

The symptoms depend on which area of the nervous system is involved. They also depend on what's causing the problem. These problems may occur slowly and cause a gradual loss of function (degenerative). Or they may occur suddenly and cause life-threatening problems (acute). Symptoms may be mild or severe. Some serious conditions, diseases, and injuries that can cause nervous system problems include:

• Blood supply problems (vascular disorders).
• Injuries (trauma), especially injuries to the head and spinal cord.
• Problems that are present at birth (congenital).
• Mental health conditions, such as anxiety disorders, depression, or psychosis.
• Exposure to toxins, such as carbon monoxide, arsenic, and lead.
• Problems that cause a gradual loss of function. Examples include:
  • Parkinson's disease.
  • Multiple sclerosis (MS).
  • Amyotrophic lateral sclerosis (ALS).
  • Alzheimer's disease.
  • Huntington's disease.
  • Peripheral neuropathies.
• Infections. These may cause swelling in the:
  • Brain (encephalitis or abscesses).
  • Membrane surrounding the brain and spinal cord (meningitis).
• Overuse of or withdrawal from prescription and non-prescription medicines, cannabis, illegal drugs, or alcohol.
• A brain tumour.
• Organ system failure. Examples include:
  • Respiratory failure.
  • Heart failure.
  • Liver failure (hepatic encephalopathy).
  • Kidney failure (uremia).
• Other conditions. Some examples include:
  • Thyroid dysfunction (overactive or underactive thyroid).
  • High blood sugar (diabetes) or low blood sugar (hypoglycemia).
  • Electrolyte problems.
  • Nutritional deficiencies. Examples are vitamin B1 (thiamine) and vitamin B12 deficiency.
  • Autoimmune diseases.

A sudden nervous system problem can cause many different symptoms. It depends on the area of the nervous system involved. Stroke and transient ischemic attack (TIA) are common examples of these acute problems. You may suddenly have one or more symptoms, such as:

• Numbness, tingling,or weakness. Or you may not be able to move a part or all of one side of the body (paralysis).
• Dimness, blurring, double vision, or loss of vision in one or both eyes.
• Loss of speech, trouble talking, or trouble understanding speech.
• Sudden, severe headache.
• Feeling dizzy or unsteady or not being able to stand or walk, especially if you also have other symptoms.
• Confusion or a change in level of consciousness or behaviour.
• Severe nausea or vomiting.

Seizures can also cause sudden changes in consciousness, feeling (sensation), emotion, or thought. Some people have abnormal body movements, such as muscle twitching. How often the seizures occur and how severe they are depend on the cause of the seizures and the area of the brain involved.

Diabetes can cause problems with balance. This can be a result of peripheral neuropathy or stroke.

Vertigo and dizziness are problems of balance and coordination. Vertigo is often caused by a medicine or a problem of the inner ear or brain. Emotional distress, dehydration, blood pressure problems, and other diseases can all make you feel dizzy.

Most headaches aren't caused by serious central nervous system problems. The pain that comes with a headache can be a throbbing or a piercing pain, such as with a migraine. Or it can be severe pain that comes and goes over several days, such as with cluster headaches. Headaches are usually caused by problems with the sinuses, scalp, or muscles of or around the head.