Cerebellar not cerebral atrophy predicts poor anti-NMDAR encephalitis outcome

By Lucy Piper

Diffuse cerebral atrophy (DCA) in patients with anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis does not necessarily mean irreversible brain damage, whereas progressive cerebellar atrophy may indicate a poor long-term prognosis, researchers report.

DCA occurred in 33% of the patients and was usually reversible, note the researchers led by Takahiro Iizuka (Kitasato University, Kanagawa, Japan) in JAMA Neurology.

Given this finding, Maarten Titulaer (Erasmus University, Rotterdam, the Netherlands) writes in a related editorial that treatment should not be withheld in anti-NMDAR encephalitis patients who develop DCA.

"Overall, the outcome is good for most patients, despite long disease duration or the need for mechanical ventilation", he says.

Among 15 patients, aged a median of 21 years, of whom 67% were female, 13 received first-line immunotherapy and four of these also received cyclophosphamide. In five patients, an ovarian teratoma was found and removed.

Magnetic resonance imaging (MRI) revealed DCA in five patients that developed 1 to 2 months after symptom onset, reaching a plateau within 6 to 16 months. These patients had significantly longer hospitalisations, required more frequent ventilator support and developed more serious complications than the remaining 13 patients without DCA.

But the researchers note that, approximately a year after symptom onset, follow-up MRI demonstrated reversal of DCA, with brain volume returning to baseline levels in up to 90 months.

And the long-term outcome, assessed after a median 68 months, was good for 13 patients, including three of the patients with DCA.

Two of these DCA patients returned to work within 3 to 5 years, one of whom continued to experience short-term memory loss after 7 years, while the other had no neurological problems 13 years on. The third patient needed bilateral above-the-knee amputation due to disseminated intravascular coagulation and was in a vegetative state for the first 18 months, but continued in employment 15 years after onset and her only neurological deficit was mild dyscalculia.

In the remaining two DCA patients outcome was poor. These individuals also developed cerebellar atrophy at about the same time as DCA and it continued to progress for more than 12 months.

The DCA partially reversed in these patients, but the cerebellar atrophy remained unchanged or progressed and, unlike DCA and other disease features, was significantly associated with poor outcome.

The two patients continued to have limb and truncal ataxia and residual cognitive deficits, the team reports, with one patient wheelchair bound and continuing to experience severe dysphonia, dysphagia, limb dystonia and slow saccade without nystagmus.

Titulaer comments that progressive cerebellar atrophy could be a biomarker for poor response in patients with anti-NMDAR encephalitis, particularly in those admitted to intensive care units (ICUs). And he stresses the need to limit the time spent in such care to avoid serious complications in these patients.

He concludes: "Physicians will agree that prompt treatment is warranted in all patients, and I advocate the use of aggressive immunotherapy if initial therapy does not lead to quick start of improvement, especially for patients in the ICU."

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