The brain and spinal cord are surrounded by a membranous covering called as the meninges. The main function of the meninges is to protect the central nervous system from any mechanical damage and also to provide a supportive network for the cranial structure. The meninges comprises of 3 layers known as dura mater, the arachnoid mater, and the pia mater present in the same order. The CSF or the cerebrospinal fluid is present in the subarachnoid space between the pia mater and the arachnoid mater. The meninges are a common site of infection called as meningitis and intracranial bleeding.
The middle layer of the meninges, also called as the arachnoid mater, lies underneath the dura mater. It has a layer of connective tissue, but it does not receive any intervention and is avascular. There is a space below the arachnoid space known as the sub-arachnoid space. The sub-arachnoid space contains the cerebrospinal fluid which acts as a cushion and protects the brain. The arachnoid mater contains small projections known as the arachnoid granulations, which project into the dura mater and allows re-circulation of the CSF through the dural venous sinuses. Due to various reasons like infection or inflammatory disease, the arachnoid mater experiences inflammation known as arachnoiditis. It can have severe symptoms and hence needs clear understanding and medical attention.
What is Arachnoiditis?
Arachnoiditis is a condition characterised by inflammation of the arachnoid mater, a layer of the meninges that surrounds and protects the brain. It is caused by infections, inflammatory diseases or neoplastic disorders. In most of the cases, this condition presents itself with stinging sensation, burning type of pain and neurological issues. There may be formation of scar tissue secondary to inflammation of the arachnoid, which in turn causes malfunctioning of the spinal nerves leading to pain and discomfort in the areas supplied by these nerves.
Clinically speaking, arachnoiditis are of multiple types as follows:
- Arachnoiditis ossificans
- Cerebral arachnoiditis
- Adhesive arachnoiditis
- Neoplastic arachnoiditis
- Postmyelographic arachnoiditis
- Optochiasmatic arachnoiditis
- Rhinosinusogenic cerebral arachnoiditis.
Symptoms of Arachnoiditis
Arachnoiditis commonly affects the nerves in the lower back and legs. The symptoms do not have any consistent pattern; however, the most common symptoms of arachnoiditis include the following:
- Pain in the lower back and lower extremities
- Weakness in legs with numbness, tingling and burning sensation
- Severe electric shock-like sensation with severe shooting pain in legs
- Twitching in legs with muscle cramps and spasms
- Issues with sexual functions, urinary issues and bowel changes
- Over a period of time, arachnoiditis may limit functions of daily activities in view of persistent pain.
Epidemiology of Arachnoiditis
It is a rare condition and generally affects the female population more than the male population. This increased incidence in female population could be because of receiving epidural injection during child birth. Being a rare condition, the exact incidence and prevalence rates are unknown. A study has shown that approximately 11,000 cases of arachnoiditis are seen every year in USA. Arachnoiditis often goes misdiagnosed or undiagnosed making it further difficult to estimate the prevalence.
Causes of Arachnoiditis
The most common causes of arachnoiditis include:
- Direct Mechanical Injury to the Spine Causing Arachnoiditis: This is often seen in repetitive spinal surgeries, spinal fusion procedures and other minimally invasive spinal procedures.
- Trauma to the spinal cord can also cause arachnoiditis
- Reaction to Chemical Agents: It has been noted that the chemical used as a dye during myelogram can cause arachnoiditis. It is a method where a dye is used as a radiographic contrast media. The contrast agent is injected around the spinal cord and nerves and can lead to irritation of the nerves in certain cases. The use of these radiographic contract media has been discontinued in view of the side effects elicited by them. The newer agents used, the safer it is and does not cause arachnoid inflammation. Studies have shown that in certain cases, epidural steroid injection may also lead to arachnoiditis.
- Infections Can Cause Arachnoiditis: Infections caused by bacteria, fungi and viruses can lead to inflammation of the arachnoid mater. This is seen in association with meningitis and tuberculosis.
- Chronic Spinal Cord Diseases: Conditions such as chronic degenerative disc disease and advanced spinal stenosis can lead to compression of the spinal nerves resulting in inflammation and arachnoiditis.
- Arachnoiditis Caused Due to Post-Surgical Complications: Invasive spinal surgeries and multiple lumbar punctures can lead to inflammation of the arachnoid leading to arachnoiditis.
- Other causes of arachnoiditis include epidural disc prolapse, manipulation during catheter insertion, spinal taps, etc.
Risk Factors of Arachnoiditis
- Arachnoiditis is commonly seen in association with infectious condition which may be bacterial, viral, fungal or parasitic in nature.
- Non-infectious condition that may cause arachnoiditis includes post-surgical complications, intrathecal haemorrhage, and reaction to myelographic contract agent, steroids and anaesthetics.
- Neoplastic conditions such as melanoma, non-Hodgkin lymphoma, breast cancer and lung cancer. It can be also seen in conditions such as choroid plexus carcinoma, medulloblastoma, ependymoma, glioblastoma multiforme etc.
Diagnosis of Arachnoiditis
Diagnosis of arachnoiditis is done by an experienced physician or a neurologist. A detailed case history is obtained followed by clinical examination. Investigative studies such as CAT scan (computerized axial tomography) and MRI (magnetic resonance imaging) are often helpful in the diagnosis of the disease. Plain x-ray is often not very helpful in diagnosis of the condition. EMG or electromyograms are often used as a confirmatory study. It helps in evaluating the nerve function and assessing the extent and severity of the nerve damage using electrical impulses.
Treatment of Arachnoiditis
Arachnoiditis does not have a specific treatment plan. Management of arachnoiditis is done symptomatically.
- Oral medications such as anti-inflammatories and muscle relaxants are often advised for management of chronic pain associated with arachnoiditis. Opioids should be used with great caution to avoid dependency and addiction.
- Intervention by a pain management specialist can also be considered for treatment and management of arachnoiditis.
- Physical manipulation by an experienced physiotherapist is quite helpful in reducing pain and improving functionality among patients suffering from arachnoiditis. Certain exercises are usually recommended based on the severity and extent of the disease.
- Psychotherapy may help is overcoming depression associated with arachnoiditis.
- Treatment by a chiropractor can also be taken into consideration.
- The main idea of the treatment for arachnoiditis is to reduce pain and improve symptoms and limit activities of daily living.
- Surgery is not recommended under normal circumstances in view of poor outcome and temporary relief in symptoms. Surgeries can also lead to scar tissue formation and fibrosis.
- A large number of studies and clinical research are been carried out for determining the benefits of electrical stimulation and steroid injection in management of arachnoiditis.
Arachnoiditis is a rare neurological condition that causes inflammation of the arachnoid mater. Arachnoid mater is a membrane of the meninges that surround and protect the brain and the spinal cord. Any inflammation in this membrane directly and indirectly can affect the nerve roots within the affected area. It is most commonly associated with pain and discomfort in the lower back area and legs. Although not life-threatening, Arachnoiditis presents itself as pain, weakness, numbness with tingling and burning sensation in the area supplied by the affected nerves. It can also alter affect urination and bowel movement. Over a period of time it can limit physical activities. Being a rare disease, this condition often goes undiagnosed or misdiagnosed. Hence, a careful examination and diagnosis by an experienced doctor is recommended.