The authors’ observations
Psychosis in the presence of white matter demyelination could be associated with autoimmune, vascular, or nutritional disturbances. Deficiencies in vitamins B6, 9, and 12 (pyridoxine, folate, cobalamin) have been shown to cause neuropsychiatric symptoms and white matter lesions.5 Low levels of vitamins B6, 9, and 12 are associated with elevated homocysteine, which can cause small vessel ischemia leading to white matter lesions similar to changes seen in vascular dementia.5 The exact pathophysiology of ADEM is unclear, however, it is thought that after an infection, antiviral antibodies cross react with autoantigens on myelin causing an autoimmune demyelinating disease. Another hypothesized mechanism is that circulating immune complexes and humoral factors increase vascular permeability and inflammation thereby opening the blood–brain barrier. Once it is open, cells such as lymphocytes, phagocytes, and microglia cause gliosis and demyelination. Case reports have described ADEM associated with psychotic features.6
Likewise, systemic lupus erythematous has been associated with psychosis and neuropsychiatric symptoms in 14% to 75% of patients. Of these patients, 40% will experience neuropsychiatric symptoms before onset of lupus symptoms.7 One study found the most common MRI finding in neuropsychiatric systemic lupus erythematous was leukoaraiosis, which appeared in 57.1% of patients.8 Ms. S’s MRI results strongly suggest a diagnosis of MS.
EVALUATION Questionable story
Ms. S appears delusional and grandiose when she meets with the psychiatry team. She states that before her hospitalization, she was an actress and could ambulate, rent a motel room, and drive a car without assistance. However, during the examination, she cannot walk without 2 staff members for support, and overall her self-reported history sounds questionable. There were several pieces of evidence that corroborate portions of her story: (1) a screen actors guild card was found among personal belongings; (2) she was transported to the ER from a local motel; (3) she had recently visited another hospital and, at that time, was deemed stable enough to be discharged.
On the Montreal Cognitive Assessment (MoCA) Ms. S scored 19/30, with deficits mainly in executive/visuospatial and delayed recall memory. An alternate form of the MoCA is administered 1 day later, and she scores 20/30 with similar deficits. After obtaining medication consent, she is given risperidone, up to 2 mg/d, and becomes more cooperative with the treatment team.
The authors’ observations
Approximately 40% to 65% of MS patients experience cognitive impairment.9 Cognitive dysfunction in a depressed patient with MS might appear as pseudo-dementia, but other possible diagnoses include:
- true dementia
- encephalitis or infection
- medication- or substance-induced.
White matter demyelination is associated with subcortical dementia, which is characterized by slowness of information processing, forgetfulness, apathy, depression, and impaired cognition. According to meta-analyses, the most prominent neuropsychological deficits in MS are found in the areas of verbal fluency, information processing speed, working memory, and long-term memory.10 Relapsing-remitting type MS patients generally have less cognitive impairment than those with the chronic progressive type of the disease.