Treatment Strategies and Managing Risks

Treating Primary Angiitis of the Central Nervous System (PACNS) is a marathon, not a sprint. Because this disease can cause permanent brain damage, the initial goal is “induction”—using powerful medications to quickly stop the inflammation—followed by “maintenance” to keep the disease in check over the long term ^[1][2].

Due to the rarity of PACNS, there is no single “one-size-fits-all” protocol. Current guidelines from the European Stroke Organisation (ESO) emphasize that treatment should be managed by a multidisciplinary team at a specialized center ^[2].

The Two Phases of Treatment

Treatment is generally divided into two distinct periods, though exact timelines vary depending on severity, organ involvement, and your individual health:

1. Induction Therapy: The goal is to achieve remission, meaning the inflammation is no longer active. An example of a common approach for adults is a combination of high-dose glucocorticoids (steroids) and cyclophosphamide ^[3][1]. Steroids often begin with a three-day intravenous “pulse” followed by oral tablets that are slowly reduced over months or a year ^[4][1]. Steroids must never be stopped abruptly.
2. Maintenance Therapy: Once the disease is quiet, your team will switch you to “steroid-sparing” agents. These are designed to keep the immune system stable while allowing you to stop or significantly lower your steroid dose. Common options include azathioprine, mycophenolate mofetil, methotrexate, or rituximab ^[1][5]. Most patients remain on maintenance therapy for an extended period, often at least 24 months, but this duration is highly individualized ^[1].

Medication Options and Vessel Size

Your treatment intensity may be tailored based on whether you have small-vessel or medium/large-vessel disease, and whether you have secondary CNS vasculitis (which may require treating the underlying condition) ^[3].

• Small-Vessel PACNS: This type often causes more severe neurological symptoms initially, such as seizures or significant cognitive decline, and may require more aggressive induction therapy even if your angiogram looks normal ^[6][7].
• Rituximab: This is increasingly used as an alternative to cyclophosphamide, especially if you have had a relapse or if you cannot tolerate traditional therapy ^[8][9]. While it avoids some cumulative cyclophosphamide exposure, it has a different risk profile that includes infusion reactions, hepatitis B reactivation, hypogammaglobulinemia, and serious infection ^[10].

Managing Risks and Monitoring for Harms

The medications used for PACNS are potent and can cause serious “side effects” (toxicities). Your care team will implement a rigorous monitoring plan to keep you safe ^[9][2]:

• Infection Risk: Because these drugs suppress your immune system, you are at a higher risk for serious infections like pneumonia or tuberculosis ^[10]. You may be conditionally prescribed a preventative antibiotic (prophylaxis) to protect against Pneumocystis jirovecii pneumonia (PJP) ^[9]. Live vaccines should typically be avoided.
• Cyclophosphamide Toxicity: This drug requires CBC, renal function, and urinalysis monitoring. Risks include hemorrhagic cystitis (bladder bleeding), low white blood cells, and a later risk of malignancy ^[9]. It also carries major risks of infertility or ovarian/testicular injury, meaning contraception and fertility preservation counseling are vital before starting. Mycophenolate and methotrexate also have major reproductive implications.
• Steroid Side Effects: Long-term steroid use requires active monitoring of blood pressure, blood glucose, eye health (cataracts, glaucoma), mood/psychosis changes, and infection risk. Your doctor will likely monitor your bone health and may recommend calcium or vitamin D to protect against weakened bones (osteoporosis) ^[1].
• Screening: Before starting treatment, you should be screened for hepatitis B and tuberculosis, as these infections can reactivate when your immune system is suppressed ^[10][11].

Evaluating Success

Your doctor will use a combination of repeat MRIs and clinical exams to determine if the treatment is working. On follow-up imaging, the inflammation in the vessel walls (enhancement) typically begins to decrease over the first year of treatment ^[12]. It is common to feel frustrated by the slow pace of recovery, but consistent adherence to your treatment plan is the best way to prevent relapses and protect your brain health ^[13][14].