The French FFI cases

Sleep architecture and sleep-disordered breathing in fatal insomnia

STUDY OBJECTIVES

Fatal insomnia (FI) is a rare prion disease severely affecting sleep architecture. Breathing during sleep has not been systematically assessed. Our aim was to characterize the sleep architecture, respiratory patterns, and neuropathologic findings in FI.

METHODS

Eleven consecutive FI patients (ten familial, one sporadic) were examined with video-polysomnography (vPSG) between 2002 and 2017. Wake/sleep stages and respiration were evaluated using a modified scoring system. Postmortem neuropathology was assessed in seven patients.

RESULTS

Median age at onset was 48 years and survival after vPSG was 1 year. All patients had different combinations of breathing disturbances including increased respiratory rate variability (RRV; n = 7), stridor (n = 9), central sleep apnea (CSA) (n = 5), hiccup (n = 6), catathrenia (n = 7), and other expiratory sounds (n = 10). RRV in NREM sleep correlated with ambiguous and solitary nuclei degeneration (r = 0.9, p = 0.008) and reduced survival (r = -0.7, p = 0.037). Two new stages, Subwake1 and Subwake2, present in all patients, were characterized. NREM sleep (conventional or undifferentiated) was identifiable in ten patients but reduced in duration in eight. REM sleep occurred in short segments in nine patients, and their reduced duration correlated with medullary raphe nuclei degeneration (r = -0.9, p = 0.005). Seven patients had REM without atonia. Three vPSG patterns were identified: agitated, with aperiodic, manipulative, and finalistic movements (n = 4); quiet-apneic, with CSA (n = 4); and quiet-non-apneic (n = 3).

CONCLUSIONS

FI patients show frequent breathing alterations, associated with respiratory nuclei damage, and, in addition to NREM sleep distortion, have severe impairment of REM sleep, related with raphe nuclei degeneration. Brainstem impairment is crucial in FI.

Fatal familial insomnia and sporadic fatal insomnia

Fatal familial insomnia (FFI) and sporadic fatal insomnia (sFI), or thalamic form of sporadic Creutzfeldt-Jakob disease MM2 (sCJDMM2T), are prion diseases originally named and characterized in 1992 and 1999, respectively. FFI is genetically determined and linked to a D178N mutation coupled with the M129 genotype in the prion protein gene (PRNP) at chromosome 20. sFI is a phenocopy of FFI and likely its sporadic form. Both diseases are primarily characterized by progressive sleep impairment, disturbances of autonomic nervous system, and motor signs associated with severe loss of nerve cells in medial thalamic nuclei. Both diseases harbor an abnormal disease-associated prion protein isoform, resistant to proteases with relative mass of 19 kDa identified as resPrP^TSE type 2. To date at least 70 kindreds affected by FFI with 198 members and 18 unrelated carriers along with 25 typical cases of sFI have been published. The D178N-129M mutation is thought to cause FFI by destabilizing the mutated prion protein and facilitating its conversion to PrP^TSE. The thalamus is the brain region first affected. A similar mechanism triggered spontaneously may underlie sFI.

Sporadic fatal insomnia with clinical, laboratory, and genetic findings

A 75-year-old man presented with a three-year history of progressively worsening insomnia and dementia. His mother and older sister had similar disorders. On initial examination, he was awake, apathetic, and disoriented but had no focal neurological deficits. Electroencephalography showed diffuse background slowing with neither periodic discharge nor sleeping activity. A single-photon emission CT scan showed significantly reduced cerebral perfusion in bilateral thalami, basal ganglia, and limbic cortices. In the late stage of his illness, he developed sphincter dysfunction. Laboratory studies showed increased T-lymphocytes and B-lymphocytes and reduced cortisol level. Cerebrospinal fluid 14-3-3 protein was absent. Genetic evaluations failed to show the aspartate to asparagine point mutation at codon 178 but disclosed an asparagine to serine substitution at codon 171 in one allele and a deletion of 24 base pairs in the other allele in the human prion protein gene. These findings led to a diagnosis of sporadic fatal insomnia, which is a recently described prion disease.

Self management of fatal familial insomnia. Part 1: what is FFI?

CONTEXT

Fatal familial insomnia (FFI) is a genetically transmitted neurodegenerative prion disease that incurs great suffering and has neither a treatment nor a cure. The clinical literature is devoid of management plans (other than palliative). Part 1 of this article reviews the sparse literature about FFI, including case descriptions. Part 2 of this paper describes the efforts of 1 patient (with the rapid-course Met-Met subtype) to contend with his devastating symptoms and improve the quality of his life.

DESIGN

Interventions were based on the premise that some symptoms may be secondary to insomnia and not a direct result of the disease itself. Strategies (derived by trial and error) were devised to induce sleep and increase alertness. Interventions included vitamin supplementation, narcoleptics, anesthesia, stimulants, sensory deprivation, exercise, light entrainment, growth hormone, and electroconvulsive therapy.

RESULTS

The patient exceeded the average survival time by nearly 1 year, and during this time (when most patients are totally incapacitated), he was able to write a book and to successfully drive hundreds of miles.

CONCLUSION

Methods to induce sleep may extend and enhance life during the disease, although they do not prevent death. It is hoped that some of his methods might inspire further clinical studies.