A new study in the Journal of the American Medical Association Neurology set out to examine the implications of the presence of a certain type of antibody in some people’s cerebrospinal fluid.

Researchers wanted to know what the existence of anti-contactin-associated protein-like 2 (anti-CASPR2) meant for patients with certain neurological syndromes, especially neuromytonia (NMT), Morvan syndrome (MoS) and limbic encephalitis.

The researchers looked back at patients who were treated at a hospital in France between 2009 and 2015—18 of whom were known to have anti-CASPR2 antibodies in their systems and 15 others who were diagnosed with NMT or MoS, all of whom were mostly male. They conducted MRI scans of the participants’ brains, collected samples of cerebrospinal fluid and analyzed their medical histories and conditions.

The researchers found certain patterns of neurological conditions among the group with anti-CASPR2 antibodies. All of them showed symptoms of limbic encephalitis, while 16 of the 18 had temporal lob seizures and 17 of them showed memory disorders. Another 12 showed extralimbic signs, and six of the 18 had cerebella ataxia. On the other hand, only two of the 18 were diagnosed with NMT.

All of them also showed IgG4 autoantibodies. Researchers followed up with 16 of those 18 patients for at least six months and found that 15 of them showed some improvement and six of them relapsed during that time.

Among the group that had been diagnosed with NMT or MoS, 14 of the 15 had temporolimbic abnormalities, according to imaging. And in all of the patients that had been diagnosed with NMT or MoS, anti-CASPR2 antibodies showed up in the serum, though not everyone showed the antibodies in the cerebrospinal fluid.

Taken together, the authors of the study concluded that patients with anti-body associated autoimmune encephalitis were the only people who were found to have anti-CASPR2 antibodies in their cerebrospinal fluid, and patients who have been diagnosed with NMT or MoS only have anti-CASPR2 antibodies show up in the serum. Both groups who show the antibodies are mostly made up of male patients.