Fig. 13.1
Relapse-free survival in PINSs and in MS: patients with PINSs, either those with isolated central damage (encephalitis, encephalomyelitis, and myelitis, red line) and the variants with additional peripheral involvement (encephalomyeloradiculitis and myeloradiculitis, green line), show a lower risk of relapses compared to multiple sclerosis (blue line); moreover, relapses in PINSs have a peculiar timeframe, occurring within the first 2 years from onset. Among PINS, forms with peripheral damage show a higher rate of relapses compared to pure central syndromes
Relapses occur after a clear-cut time of neurological stabilization and should not be confused with “rebounds” or “pseudo-relapses”: the latter are neurological fluctuations due to reactivation of the same lesions, related to steroid discontinuation, typically occurring within 1–3 months from disease onset.
Relapses are classified as follows:
Recurrent-PINS, when the new event is a recurrence of the initial symptoms, with or without imaging enlargement or new enhancement of the original lesion, and no new MRI lesions.
Multiphasic-PINS, when the new event affects different anatomic areas; MRI must show new areas of involvement, but also demonstrate complete or partial resolution of those lesions associated with the first event.
In Pediatric criteria, the occurrence of a multiphasic course is accepted for disseminated forms only, and provided that, again, the onset is polysymptomatic with encephalopathy.
The frequency of relapses is 10–30 %, with recurrent forms >>> than multiphasic; variants with peripheral involvement have a higher risk of relapses.
13.10.2 Mortality and Disability
While historical groups showed mortality rates reaching 30 %, mortality rate is <5 % in recent series, probably due to improved early recognition of the disease, treatment with steroids, and change in supportive care. Thus, despite the severity characterizing the acute phase, the mortality rate is relatively low. Causes of death include sepsis and pneumonia; but among those directly related to PINS, there is respiratory failure due to brainstem involvement, raised intracranial pressure, uncontrolled seizures, and cardiovascular autonomic dysfunction.
13.10.2.1 Disability
A high proportion of residual disability occurs.
The average time to recovery ranges from 1 to 6 months, although full recovery or stabilization of deficits may occur for up to 2 years, especially in variants with spinal cord or peripheral involvement.
The spectrum of recovery spreads from childhood encephalomyelitis and encephalitis, with complete recovery in 80–90 % of cases, to adult/elderly transverse myelitis and myeloradiculoneuritis, which shows the worst outcome, not only in terms of residual disability (severe in 60 %), but also for steroid resistance (60 %) and risk of relapse (40 %).
Independent of the clinical form (with or without myelitis or peripheral involvement), the outcome is worse for adults than for childhood series with respect to hospitalization, ICU admissions, and recovery. Both in children and adults, isolated myelitis are accompanied by more severe outcomes compared to myelitis occurring in the context of encephalomyelitis; again, myelitis have better outcome in children compared to adults (Table 13.1) (however, during the acute phase, the neurological dysfunction may be more severe in children).
Table 13.1
Main outcome parameters in childhood and adult series, divided in three main PINS forms: encephalomyelitis, myelitis, and forms complicated by peripheral involvement
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