Case Report: Osmotic Demyelination Syndrome in an Adolescent with Neuromyelitis Optica

Associations between neuromyelitis optica spectrum disorder, Sjögren's syndrome, and conditions with electrolyte disturbances

OBJECTIVE

Electrolyte disorders are among the important conditions negatively affecting the disease course of neuromyelitis optica spectrum disorder (NMOSD). Possible mechanisms may include renal tubular acidosis (RTA) accompanying Sjögren's syndrome (SS), syndrome of inappropriate antidiuretic hormone secretion (SIADH), and central diabetes insipidus (DI). Currently, the overlap profiles between these conditions remain uncertain.

METHODS

This cross-sectional study collected data from the nationwide administrative Diagnosis Procedure Combination (DPC) database and evaluated the overlap profiles.

RESULTS

Among the 28,285,908 individuals from 1203 DPC-covered hospitals, 8477 had NMOSD, 174108 had SS, 4977 had RTA, 7640 had SIADH, and 24,789 had central DI. Of those with NMOSD, 986 (12%) had SS. The odds ratio (OR) for a diagnosis of NMOSD in those with SS compared with those without was 21 [95% confidence interval (CI), 20-23]. Overlap between NMOSD and SS was seen both in males (OR, 28 [95% CI, 23-33]) and females (OR, 16 [15-17]) and was more prominent in the younger population. Among patients with SS, the prevalence of RTA was lower in patients with NMOSD compared with those without NMOSD. Patients with NMOSD showed a higher prevalence of SIADH (OR, 11 [7.5-17]; p < 0.0001) and DI (OR, 3.7 [2.4-5.3]; p < 0.0001). Comorbid SS in NMOSD was associated with a higher prevalence of DI.

CONCLUSIONS

Patients with NMOSD are likely to have SS, SIADH, and central DI. RTA in SS does not facilitate the overlap between NMOSD and SS. SS in NMOSD may predispose patients to DI.

A novel association of osmotic demyelination in Sjögren's syndrome prompts revisiting role of aquaporins in CNS demyelinating diseases: A literature review

BACKGROUND

Primary Sjögren's syndrome (SS) is a chronic systemic autoimmune disease with varied neurological manifestations. SS is associated with anti-aquaporin-4 antibody (AQP4-IgG)-positive neuromyelitis optica spectrum disorder (NMOSD), a demyelinating autoimmune disorder of the central nervous system (CNS). Intriguingly, there are reports of osmotic demyelinating syndrome (ODS), a supposedly non-inflammatory disorder, in the context of SS and renal tubular acidosis (RTA), both of which are not yet established risk factors for ODS.

METHODS

A literature search was undertaken to identify case reports of ODS in patients with SS. Details of the clinical and laboratory features of these patients were compiled. Additionally, we searched for NMOSD in patients with SS. We looked for co-existing RTA in patients with SS-ODS as well as SS-NMOSD. We also screened for reports of ODS in RTA without underlying SS.

RESULTS & DISCUSSION

We identified 15 patients (all women, median age 40 years) with ODS in SS, and all of these patients had comorbid RTA. There were only three reported cases of ODS in RTA without underlying SS. We identified a total of 67 patients with SS-NMOSD, of whom only 3 (4.5%) had RTA. Hence, unlike NMOSD, the development of ODS in SS requires a prolonged osmotic or electrolyte abnormality caused by the comorbid RTA. The 15 patients with ODS and SS -RTA, showed heterogeneous clinical manifestations and outcomes. The most common symptom was quadriparesis, seen in 14 of the 15 patients. Eleven of the 15 patients had one of the following features, either alone or in combination: worsening of the sensorium, extensor plantar response, dysphagia/dysarthria, and facial palsy. The latter four manifestations were present at the onset in 7 patients and later in the course of the illness in the remaining 4 patients. Ocular palsy was seen in only four of the 15 patients and was a late manifestation. One patient who had extensive long-segment myelitis and subsequent ODS died, but most patients recovered without significant sequelae. None had hyponatremia, while all patients had hypokalemia and/or hypernatremia. Hypokalemia causing nephrogenic diabetes insipidus (NDI) followed by rapid rise in sodium and the resultant osmotic stress could potentially explain the occurrence of ODS in SS-RTA. Aquaporin (AQP) in astrocytes is implicated in ODS, and renal AQP is downregulated in NDI. Antibodies against AQPs are present in some patients with SS. Defective AQP is therefore a common link underlying all the connected diseases, namely SS, NDI, and ODS, raising the possibility of immune-mediated AQP dysfunction in the pathogenesis.

CONCLUSION

The hitherto unreported association between SS-RTA and ODS may implicate SS and/or RTA in the development of ODS. In the setting of SS-RTA, ODS must be suspected when a patient with flaccid quadriparesis does not respond to the correction of potassium or develops additional neurological features along with a rise in sodium. Defective functions of AQPs may be a possible mechanism linking demyelinating CNS lesions, SS, and RTA. Studies evaluating AQP functions and serum antibodies against AQPs in these conditions are warranted.

Jaw clonus in neuromyelitis optica spectrum disorder with subsequent osmotic demyelination syndrome

Jaw clonus, a fascinating, yet uncommon clinical sign, is suggestive of supranuclear lesions of the trigeminal nerve. It has previously been reported in association with amyotrophic lateral sclerosis. Hereby, we report an index case of jaw clonus in a patient of neuromyelitis optica spectrum disorder with subsequent osmotic demyelination syndrome with pseudobulbar palsy due to the involvement of pontine corticobulbar fibres.