For mild neurocognitive disorder due to prion disease, code 331.83 (631.84). (Note: Do not use the additional code for prion disease. Behavioral disturbance cannot be coded but should still be indicated in writing.)
The classification of major or mild neurocognitive disorder (NCD) due to prion disease in- cludes NCDs due to a group of subacute spongiform encephalopathies (including Creutz- feldt-Jakob disease, variant Creutzfeldt-Jakob disease, kuru, Gerstmann-Straussler-
Scheinker syndrome, and fatal insomnia) caused by transmissible agents known as prions.
The most common type is sporadic Creutzfeldt-Iakob disease, typically referred to as
Creutzfeldt-Jakob disease (CID). Variant CID is much rarer and is associated with trans- mission of bovine spongiform encephalopathy, also called "mad cow disease." Typically, individuals with CID present with neurocognitive deficits, ataxia, and abnormal move- ments such as myoclonus, chorea, or dystonia; a startle reﬂex is also common. Typically, the history reveals rapid progression to major NCD over as little as 6 months, and thus the disorder is typically seen only at the major level. However, many individuals with the dis- order may have atypical presentations, and the disease can be confirmed only by biopsy or at autopsy. Individuals with variant CID may present with a greater preponderance of psychiatric symptoms, characterized a by low mood, withdrawal, and anxiety. Prion dis- ease is typically not diagnosed without at least one of the characteristic biomarker fea- tures: recognized lesions on magnetic resonance imaging with DWI (diffusion-weighted imaging) or FLAIR (ﬂuid-attenuated inversion recovery), tau or 14-3-3 protein in cerebro- spinal ﬂuid, characteristic triphasic waves on electroencephalogram, or, for rare familial forms, family history or genetic testing.
The annual incidence of sporadic CID is approximately one or two cases per million peo- ple. Prevalence is unknown but very low given the short survival.
Prion disease may develop at any age in adults—the peak age for the sporadic CID is ap- proximately 67 years—although it has been reported to occur in individuals spanning the teenage years to late life. Prodromal symptoms of prion disease may include fatigue, anx- iety, problems with appetite or sleeping, or difficulties with concentration. After several weeks, these symptoms may be followed by incoordination, altered vision, or abnormal gait or other movements that may be myoclonic, choreoathetoid, or ballistic, along with a rapidly progressive dementia. The disease typically progresses very rapidly to the major level of impairment over several months. More rarely, it can progress over 2 years and ap- pear similar in its course to other NCDs.
Environmental. Cross-species transmission of prion infections, with agents that are closely related to the human form, has been demonstrated (e.g., the outbreak of bovine spongiform encephalopathy inducing variant CID in the United Kingdom during the mid- 19905). Transmission by corneal transplantation and by human growth factor injection has been documented, and anecdotal cases of transmission to health care workers have been reported.
Genetic and physiological. There is a genetic component in up to 15% of cases, associ- ated with an autosomal dominant mutation.