What Do CSF and Spinal Tap Results Show for SREAT?

A lumbar puncture (spinal tap) is an important step in evaluating suspected Steroid-Responsive Encephalopathy Associated with Autoimmune Thyroiditis (SREAT), also known as Hashimoto’s encephalopathy. The test is one component of a broader evaluation. It helps doctors look for signs of inflammation in your central nervous system and is crucial for helping to evaluate other serious conditions like infections or different types of autoimmune encephalitis.

Signs of Inflammation

When doctors analyze your cerebrospinal fluid (CSF)—the clear liquid that surrounds and protects your brain and spinal cord—they are looking for specific markers that might suggest an active immune response. Because SREAT is a rare condition, there is no single spinal fluid result that confirms the diagnosis. Instead, doctors commonly look for clues such as:

• Elevated protein: This is the most common abnormality reported in small studies of SREAT, appearing in roughly 70% to 90% of cases ^[1][2]. However, high protein is nonspecific and can be caused by many things, including age, other neurological conditions, or even a difficult spinal tap procedure ^[3].
• White blood cells (Pleocytosis): Small case studies suggest about one-third of people with SREAT will have a mildly elevated number of white blood cells in your spinal fluid ^[1][3]. These are usually lymphocytes, a type of immune cell ^[4].
• Oligoclonal bands: These are specific protein patterns that suggest your immune system might be producing antibodies within the central nervous system. To interpret this correctly, doctors must compare your spinal fluid to a paired blood sample. While their presence can support the idea of inflammation, they are nonspecific and do not confirm SREAT ^[5].

The Goal: Evaluating Other Causes

Because SREAT shares symptoms with many other neurological diseases, a major role of the spinal tap is to help determine if your symptoms are caused by something else. High thyroid antibodies in the blood are common in the general population, so doctors must ensure those antibodies aren’t just a coincidence ^[5][6].

To do this, your spinal fluid is tested to help evaluate:

• Infections: Doctors will test your fluid for viruses (like herpes simplex), bacteria, and other pathogens ^[7][8]. While a negative result lowers the suspicion of these dangerous infections, it does not completely rule them out, especially early in an illness. Doctors will interpret these results alongside your symptoms, brain imaging, and blood tests.
• Other Autoimmune Diseases: Sometimes, a person with high thyroid antibodies actually has a different, highly specific type of autoimmune encephalitis, such as anti-NMDA receptor encephalitis ^[9][10]. Targeted testing of the spinal fluid may help identify these specific brain antibodies, leading to a more precise diagnosis ^[11].

What if My Results Are Normal?

It is completely possible to have SREAT and have perfectly normal spinal fluid ^[12][13]. A normal result does not mean your symptoms aren’t real, nor does it exclude an SREAT diagnosis ^[14].

Instead, a normal spinal tap is helpful because it lowers the likelihood of certain infections and alternative autoimmune diseases that often cause spinal fluid abnormalities. Your care team will look at your normal spinal tap alongside your clinical symptoms, blood tests, and brain imaging to build a complete picture of your health.

Safety Note: If you or your loved one experience worsening confusion, new seizures, reduced consciousness, severe headache, or fever, seek urgent medical care. Do not wait for a spinal fluid interpretation to get help.