Arachnitis: Symptoms, Types, Causes and Treatment

Arachnitis, often referred to as arachnoiditis, is a rare but serious medical condition characterized by inflammation of the arachnoid mater—the delicate membrane that surrounds the brain and spinal cord. This inflammation can result in persistent pain, neurological deficits, and a range of other symptoms, impacting quality of life significantly. Understanding arachnitis requires a look at its clinical presentation, different types, underlying causes, and available treatment options. This article provides an in-depth, evidence-based guide to help patients, caregivers, and healthcare professionals recognize and manage this challenging condition.

Symptoms of Arachnitis

Arachnitis can manifest in a variety of ways, depending on the severity and location of the inflammation. Recognizing these symptoms early is crucial for effective management and improved outcomes. The clinical presentation can be subtle or dramatic, often mimicking other neurological conditions.

Symptom	Description	Example Presentation	Source(s)
Pain	Severe, persistent, neuropathic pain	Burning, electric-shock-like	1,2,4
Neurological Deficits	Weakness, sensory changes, paralysis	Lower limb weakness, numbness	1,2,3
Sensory Changes	Dysesthesia, hypoesthesia, allodynia	Tingling, altered sensation	2,4
Visual Loss	Vision impairment or blindness	Progressive vision loss	3
Headache	Persistent or severe headache	Associated with other symptoms	3
Autonomic Dysfunction	Amenorrhea, bowel/bladder issues	Menstrual changes, incontinence	3

Table 1: Key Symptoms

Pain and Sensory Disturbances

One of the hallmark features of arachnitis is severe, often neuropathic pain. Patients may describe this as burning, tingling, or electric-shock-like sensations. The pain is usually persistent and can radiate from the site of inflammation to other parts of the body. For example, in spinal arachnoiditis, intense pain may spread down the legs, sometimes accompanied by numbness or allodynia (pain from stimuli that shouldn’t normally cause pain) 1,2,4.

Neurological Deficits

As the inflammation progresses, it can lead to neurological deficits such as weakness, particularly in the lower limbs. Some patients experience progressive difficulties with walking, coordination, or even paralysis. The extent of these deficits often depends on the region of the nervous system involved. For example, lumbar or lumbosacral arachnoiditis commonly affects the legs due to involvement of the cauda equina 2.

Sensory Changes

Dysesthesia (abnormal sensation), hypoesthesia (reduced sensation), and allodynia are frequently reported. Patients may also report tingling, pins-and-needles, or feelings of numbness in affected areas 2,4.

Visual and Autonomic Symptoms

In rare cases, such as optochiasmatic arachnoiditis, patients may experience progressive loss of vision, headaches, and even hormonal changes such as amenorrhea (absence of menstrual periods) 3. These symptoms reflect inflammation in regions adjacent to the optic chiasm and hypothalamus.

Additional Manifestations

In some cases, arachnitis may lead to complications such as syringomyelia (development of fluid-filled cysts in the spinal cord), which can further exacerbate neurological symptoms 2,5.

Types of Arachnitis

Arachnitis is not a one-size-fits-all diagnosis. Several distinct types exist, each with unique features based on the location, cause, and nature of the inflammation. Understanding these types helps in tailoring diagnosis and treatment.

Type	Region Affected	Typical Features	Source(s)
Spinal Arachnoiditis	Spine (lumbar, thoracic)	Radicular pain, weakness	1,2,5
Optochiasmatic	Optic chiasm/brain	Visual loss, headache, amenorrhea	3
Adhesive Arachnoiditis	Spinal/cranial nerves	Nerve root clumping, fibrosis	1,2
Postinfectious	Variable	Follows infection, variable	5,6
Chemical/Mechanical	Variable	After surgery, trauma, myelogram	1,5

Table 2: Major Types of Arachnitis

Spinal Arachnoiditis

This is the most common form and typically involves the lower back (lumbar or lumbosacral spine). It manifests as radicular pain (pain radiating along nerve roots), lower limb weakness, and sometimes bowel or bladder dysfunction. Severe cases may develop into cauda equina syndrome or progress to syringomyelia 1,2,5.

Optochiasmatic Arachnoiditis

A rare but serious type, optochiasmatic arachnoiditis affects the optic chiasm and nearby brain structures. It is characterized by progressive visual loss, headaches, and hormonal disturbances such as amenorrhea. Prompt recognition is vital due to the risk of permanent vision loss 3.

Adhesive Arachnoiditis

This subtype is marked by the formation of fibrous adhesions and scarring within the arachnoid mater, leading to nerve root clumping and sometimes deformity of the dural sac. It can be a consequence of inflammation from multiple causes, including surgery, infection, or chemical irritation 1,2.

Postinfectious Arachnoiditis

Following infections such as meningitis or tuberculosis, the arachnoid mater can become chronically inflamed. This type may present acutely or develop insidiously, often leading to syringomyelia or other complications 5,6.

Chemical and Mechanical Arachnoiditis

Exposure to neurotoxic substances (such as oil-based contrast dyes used in myelograms), surgical interventions, or trauma can trigger inflammation of the arachnoid mater. The resulting symptoms can be similar to those seen in other types but may present more acutely 1,5.

Causes of Arachnitis

Arachnitis can arise from a variety of triggers, which are broadly categorized as infectious, chemical, mechanical, or idiopathic (unknown cause). Identifying the underlying cause is an important step in managing the disease and preventing recurrence.

Cause Type	Example Triggers	Typical Scenario	Source(s)
Infectious	Meningitis, tuberculosis, bacteria	Post-meningitis, TB arachnoiditis	2,5,6
Chemical	Myelogram dyes, corticosteroids	Post-procedure inflammation	1,5
Mechanical	Surgery, trauma, spinal injections	Post-surgical complications	1,2,5
Autoimmune/Idiopathic	Unknown, immune-mediated	No clear trigger	5

Table 3: Common Causes of Arachnitis

Infectious Causes

Infections remain a significant cause of arachnitis, particularly bacterial and tubercular meningitis. These infections can directly inflame the arachnoid mater or trigger a delayed immune response that leads to chronic inflammation. Postinfectious arachnoiditis can develop weeks to months after the initial infection 2,5,6.

Chemical Causes

Exposure to certain chemicals, notably oil-based contrast agents used in myelograms, can provoke severe arachnoid inflammation. Other neurotoxic or neurolytic substances, and even some drugs administered into the spinal canal (such as corticosteroids), have been implicated 1,5.

Mechanical Causes

Physical trauma to the spine, such as that incurred during surgery, spinal anesthesia, or repeated lumbar punctures, can initiate arachnoiditis. Surgical interventions, especially those involving the dural sac or nerve roots, are recognized risk factors 1,2,5.

Autoimmune and Idiopathic Causes

In some cases, arachnitis develops without a clear infectious, chemical, or mechanical trigger. These cases may be due to autoimmune processes or remain idiopathic. The unpredictable nature of these cases can complicate diagnosis and management 5.

Treatment of Arachnitis

Managing arachnitis is complex, as the condition is often chronic and may not respond well to conventional therapies. Treatment must be individualized based on the underlying cause, severity, and presence of complications such as syringomyelia.

Treatment Type	Example Treatments	Notes on Effectiveness	Source(s)
Medical	Corticosteroids, immunosuppressants	Variable efficacy, may reduce inflammation	3,6
Antimicrobial	Antibiotics, antitubercular agents	For infectious causes only	2,6
Surgical	Laminectomy, adhesiolysis, shunting	For severe or refractory cases	2,3,5
Symptomatic	Analgesics, neuropathic pain agents	Pain management, lidocaine patches	4

Table 4: Main Treatment Approaches

Medical Management

Corticosteroids are frequently used to suppress inflammation, especially in the acute phase or when the disease is immune-mediated. However, not all patients respond adequately, and long-term use can have significant side effects 3,6. In refractory cases, immunosuppressive agents such as cyclophosphamide have shown promise, particularly in post-tubercular and optochiasmatic arachnoiditis. Some patients experience significant improvements in neurological function after such therapy 3,6.

Antimicrobial Therapy

When an infectious cause is identified, targeted antimicrobial treatment is essential. For example, in bacterial arachnoiditis, appropriate antibiotics are required, while tuberculosis-related cases need antitubercular therapy (ATT) 2,6. Sometimes, these must be combined with corticosteroids or immunosuppressants to address persistent inflammation.

Surgical Interventions

Surgery may be needed in patients with severe symptoms, structural complications, or when conservative management fails. Procedures include laminectomy (removal of part of the vertebra), lysis of adhesions (cutting fibrous bands), and shunt placement for syringomyelia (to divert fluid and relieve pressure) 2,3,5. Outcomes are variable; surgery may relieve symptoms temporarily or halt disease progression in selected cases.

Symptomatic and Supportive Care

Pain control is a cornerstone of arachnitis management. Neuropathic pain agents (like gabapentin or pregabalin), lidocaine patches, and even physical therapy can help improve quality of life 4. In cases of severe localized neuropathic pain following spider bites (arachnidism), topical lidocaine has been effective 4. Psychological support and rehabilitation are also important for long-term management.

Conclusion

Arachnitis is a complex, multifaceted condition that can severely impact patients’ lives. Prompt recognition, identification of the underlying cause, and individualized treatment are key to optimizing outcomes.

Key Points:

• Symptoms are highly variable but often include chronic pain, neurological deficits, and sensory changes.
• Types range from spinal and optochiasmatic arachnoiditis to adhesive and postinfectious forms, each with unique features.
• Causes include infections, chemical exposures, mechanical trauma, and sometimes unknown factors.
• Treatment is challenging, requiring a combination of medical, surgical, and supportive therapies tailored to the individual.

Ongoing research and multidisciplinary care are vital for improving diagnosis, treatment, and quality of life for those affected by this rare but debilitating disease.