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Infectious pathogens like viruses and bacteria aren’t the only cause of meningitis. The brain’s protective membranes – the meninges – can also become inflamed for non-infectious reasons, called non-infectious meningitis. In a UK study of 638 meningitis patients, it was found that 16% had bacterial meningitis, 36% had viral meningitis (most of these cases were caused by VSV – varicella zoster virus – and HSV – herpes simplex viruses), 6% were non-infectious cases of meningitis and 42% had an unknown cause.
All types of meningitis are classified as either infectious or non-infectious. With infectious meningitis, pathogens have invaded the meninges and caused infection and inflammation. Non-infectious meningitis is a result of an injury or disease.
This article will tell you all you need to know about non-infectious meningitis. For more general information about meningitis, check out this article.
What is non-infectious meningitis?
The spinal cord and brain are enveloped in three tissue layers called the meninges. In between the inner layer and middle layer is the subarachnoid space, which is filled with CSF (cerebrospinal fluid). This flows through the layers and fills the brain spaces, helping to cushion the spinal cord and brain.
When the layers of tissue covering the spinal cord and brain (the meninges) and the subarachnoid space (fluid-filled space in between the meninges) become inflamed and the cause isn’t down to a pathogen, we can say it is non-infectious meningitis.
This can be caused by existing medical problems, disorders and non-infectious diseases, as well as by vaccines or drugs.
Non-infectious meningitis is aseptic meningitis, and it is an uncommon cause of the condition. Some of the main culprits that result in non-infectious meningitis are medical conditions that already cause inflammation in other parts of the body, like autoimmune conditions. Some examples include erythematosus (lupus), systemic lupus, and rheumatoid arthritis.
NSAIDs (nonsteroidal anti-inflammatory drugs) like ibuprofen can also cause non-infectious meningitis, as can some types of antibiotics.
What causes non-infectious meningitis?
There are different causes of non-infectious meningitis. Here are some of them:
Some medicines or substances have been known to induce chemical meningitis. This is a rare medical condition referred to as ‘sterile meningitis’ because there are no pathogens found in the cerebrospinal fluid (CSF).
Drugs like some cancer medications have been known to cause the condition, as have contrast dyes used in x-rays. It also forms after patients have undergone neurosurgery.
If a patient has a benign brain tumour that ruptures, droplets of fat can leak into the space between the brain and the skull, causing chemical meningitis. This type of non-infectious meningitis doesn’t often need treatment and can resolve itself.
Some patients may need treatment, however. This will depend on what has caused the meningitis. It could be that they need steroids to reduce inflammation or surgery to remove a tumour.
Carcinomatous or malignant meningitis
This is a rare type of meningitis that only affects people with solid tumours as a result of cancer like breast cancer, melanoma or lung cancer. Less than 5% of people with these conditions will develop carcinomatous meningitis though.
If the person’s cancer has spread to the CNS (central nervous system), it can cause carcinomatous or malignant meningitis. To treat the condition, doctors need to address the cancer that’s caused it with chemotherapy.
Though this type of meningitis has been caused by a pathogen (a type of fungus), it is non-contagious. It typically affects those who are taking immunosuppressive medication, for example, HIV-positive patients. The fungus is found in bird droppings and soil but ordinarily wouldn’t affect your health unless you have pre-existing conditions that weaken your immune system.
Anatomical defects often play a role in recurrent meningitis. If patients suffer recurrent meningitis, then it is recommended they be checked for anatomical defects.
Some anatomical defects that can cause meningitis include acquired structural defects which mean the paranasal sinuses or middle ear don’t communicate well with the skin and subarachnoid space.
Other anatomical defects that increase the risk include meningocele (when the meninges protrude through the spine caused by a congenital defect), skull base defects, inner ear abnormalities, neurenteric cysts (rare spinal cysts), and dermal sinus and epidermoid/dermoid cysts.
Brain surgery or a head injury
In brain surgery, the open wounds can make it easier for meningitis-causing bacteria and pathogens to enter the meninges. So, although the patient will develop bacterial meningitis, its cause will be the brain surgery.
A severe head injury could also lead to inflammation and non-infectious meningitis.
Underlying medical conditions
Non-infectious meningitis can occur when a person has an existing inflammatory disorder.
- Lupus or systemic lupus erythematosus (SLE)
Lupus and systemic lupus erythematosus (SLE) can both cause meningitis. SLE is an autoimmune disease that presents psychiatric and neurological manifestations. Meningitis with SLE is rare and less than 2% of patients with the condition will develop it.
- Sjögren’s syndrome
Sjögren’s syndrome is a chronic autoimmune condition that causes dryness in the upper respiratory tract, nose, skin, eyes, mouth and vagina. It is caused by white blood cells infiltrating exocrine tissues like tear glands and saliva glands and mistakenly attacking them.
This condition is closely associated with SLE as well as rheumatoid arthritis, and primary biliary cholangitis. Ninety per cent of people with Sjögren’s are female.
- Primary angiitis of the central nervous system
Primary angiitis of the central nervous system, or PACNS, is a rare disease that affects the spinal cord and brain. The main manifestations are seizures, headaches, encephalopathy and stroke.
This is a rare disease that causes granulomas or small, swollen areas of tissue to grow in the organs. It most often affects the lymph nodes, lungs and skin. Many people with this disease see their symptoms improve within months to years, without treatment.
- Behçet’s disease
This is a rare condition that isn’t well understood. It results in blood vessel and tissue inflammation. It causes blurred vision, mouth ulcers, genital ulcers, acne-like spots, swollen, painful and stiff joints, and headaches.
- Brain cyst ruptures
If a brain cyst is present and ruptures causing fluid to leak into the subarachnoid space, this can cause non-infectious meningitis. The cysts could be congenital or be caused by cysticercosis, an infection caused by tapeworms.
Carcinomatous meningitis (CM) is rare, and it occurs during the late stages of cancer. It occurs when the cancer cells break off from the tumour and get into the meninges. It happens in around 4% to 15% of all solid tumour cancers.
Signs and symptoms of non-infectious meningitis
No matter the cause of meningitis or the type, the symptoms are the same.
Here are some signs to look out for in non-infectious meningitis.
- Stiff neck – it is painful to put your chin towards your chest.
- Confusion/altered mental status.
- Photophobia (being sensitive to light).
With non-infectious meningitis, the symptoms are generally milder than with other types of meningitis, but it can vary. The symptoms often come on more slowly too.
Most people recover from this type of meningitis within a couple of weeks.
How is non-infectious meningitis diagnosed?
Like other types of meningitis, non-infectious meningitis is diagnosed by clinical presentation and confirmed by a lumbar puncture and analysis of the CSF (cerebrospinal fluid).
A doctor will usually suspect or be wary of meningitis when people present with a headache, stiff neck and fever. They will then try to work out whether it is viral, bacterial, fungal or non-infectious meningitis.
After the lumbar puncture (or spinal tap, as it is often referred to), the cerebrospinal fluid is tested. The results will analyse the glucose and protein levels as well as the type and number of white blood cells in the sample.
It is then cultured to rule out bacterial meningitis. With non-infectious meningitis, the CSF might contain lymphocytic or neutrophilic pleocytosis and elevated protein. The glucose level is typically normal. If the fluid contains no bacteria or other infectious organisms but does contain excess white blood cells, this indicates non-infectious meningitis. The raised level of white blood cells indicates inflammation.
Often, an MRI (magnetic resonance imaging) or CT (computed tomography) scan is carried out before the lumbar puncture. This is to rule out a mass or cyst in the brain. If there is such an occurrence, a lumbar puncture can be dangerous as it could cause brain herniation, which is life-threatening.
How is non-infectious meningitis treated?
If a patient is really ill, doctors will start treating the meningitis straight away without determining its cause. This means that antibiotics will be given just in case it is caused by bacteria. Bacterial meningitis has the highest fatality rate and is the most dangerous, so it’s worth treating potential meningitis with antibiotics before waiting for the cause to be determined.
Time is of the essence in these cases and a delay in treatment can cause permanent damage. Patients might also be given an antiviral drug like acyclovir in case the disease is caused by a viral infection like HSV (herpes simplex virus).
Once the cause has been determined, the treatment will be more targeted. If no bacteria or virus has been found, the antibiotics and antiviral drugs will be stopped.
With cases of non-infectious meningitis, it’s important for doctors to work out the underlying cause. With the cause known, treatment can be decided appropriately. This might mean removing a drug or medicine. If the cause is due to cancer either in the brain or elsewhere in the body, this might be treated with chemotherapy and/or surgery.
What’s more, managing meningitis is all about focusing on care that reduces fever, ensures that fluids are given, and that the person is able to breathe properly.
Can non-infectious meningitis be prevented?
Unlike some types of bacterial meningitis, you cannot vaccinate against non-infectious meningitis. It is challenging to prevent because infection is not the cause. Being non-infectious means that it is not contagious and so you don’t need to worry about catching it off someone who has it.
Due to the variety of different causes, it is impossible to avoid. So, if you are at risk because you have underlying conditions like SLE or other autoimmune conditions, it’s important to recognise the signs and symptoms and know when to seek medical attention.
Long-term effects of non-infectious meningitis
Most people who have non-infectious meningitis make a full recovery within a matter of weeks. There can be some long-lasting persistent effects, however.
- Poor concentration.
- Persistent sensitivity to light.
- Impaired balance.
- Impaired coordination.
- Dizziness and vertigo.
- Behavioural deficits.
- Learning difficulties.
- Memory problems.
The best way to prevent complications like these is to seek medical attention as soon as possible when meningitis symptoms are present. The earlier the cause is found, the better the outlook.
Final thoughts on ‘What is non-infectious meningitis?’
Non-infectious meningitis can be a serious illness. It is an inflammation of the meninges, which are the layers surrounding the brain, and the cerebrospinal fluid (CSF). Unlike infectious meningitis, this can be caused by many possible reasons, including a reaction to medication, a complication of advanced cancer, or as a result of brain surgery.
As the symptoms of all types of meningitis are similar, it’s important to find out the cause. Anyone who experiences light sensitivity (photophobia), fever, a headache and a stiff neck, should be tested for meningitis. Even if the patient has non-infectious meningitis, they will usually be given antibiotic treatment before the cause is confirmed.
This is because bacterial meningitis is very dangerous and can cause permanent brain damage and there can be a need for limbs to be amputated. Sometimes it is also fatal.
When infectious meningitis has been ruled out, the doctors will try to work out what is causing the non-infectious meningitis. Patients will be treated accordingly. If their meningitis has been drug-induced, then alternative medications will be looked at.
As well as treating the cause of the problem, doctors will make patients more comfortable by giving them intravenous fluids, assisting with breathing (if necessary) and providing supportive care. Patients will also be given medicine to reduce their fever, like paracetamol.