Multiple Sclerosis (MS): Given the presence of small vessel disease findings, suspected perimenopause, and a history of anxiety, MS is a strong consideration. MS can present with a wide range of neurological symptoms, including those that mimic small vessel disease, and is more common in females. The patient's age and gender also align with the typical demographic for MS diagnosis.

Systemic Lupus Erythematosus (SLE): SLE can cause small vessel disease and is associated with various autoimmune manifestations, including those that might mimic or exacerbate anklosing spondylitis. It also has a higher prevalence in females and can present with psychiatric symptoms such as anxiety and panic attacks.
Antiphospholipid Syndrome (APS): APS can cause small vessel disease and is associated with an increased risk of thrombosis. It can also present with neurological symptoms and has a higher prevalence in females, especially those with other autoimmune diseases.
Fibromyalgia: Given the patient's history of anxiety, panic attacks, and anklosing spondylitis, fibromyalgia is a consideration. It can present with widespread pain, fatigue, and cognitive difficulties, which might be exacerbated by or contribute to the patient's anxiety and panic symptoms.

Vasculitis (e.g., Giant Cell Arteritis, Polyarteritis Nodosa): Although less common, vasculitis can cause small vessel disease and must be considered due to its potential for serious complications if left untreated. The presence of anklosing spondylitis, an autoimmune condition, slightly increases the likelihood of another autoimmune condition like vasculitis.
Cerebral Vasculitis: This is a rare but potentially deadly condition that could explain the small vessel disease findings. It requires prompt diagnosis and treatment to prevent serious neurological sequelae.
Thrombotic Thrombocytopenic Purpura (TTP): A rare disorder of the blood-coagulation system, causing extensive microscopic thrombi to form in the smallest blood vessels throughout the body. It's crucial to consider due to its high mortality rate if not treated promptly.

Susac Syndrome: A rare condition characterized by small vessel disease affecting the brain, retina, and inner ear, leading to a variety of symptoms including vision loss, hearing loss, and neurological deficits. It's more common in young women.
Primary Central Nervous System Vasculitis (PCNSV): A rare form of vasculitis that exclusively affects the vessels of the central nervous system, presenting with a wide range of neurological symptoms. It's essential to consider due to its potential for severe neurological damage if not treated.