RESIDENT & FELLOW SECTION Clinical Reasoning: Section Editor A 54-year-old woman with dementia, John J. Millichap, MD myoclonus, and ataxia Farwa Ali, MBBS SECTION 1 products, and drank 3–4 alcoholic beverages per Joseph A. Murray, MD A 54-year-old woman was referred for a second opin- week. Her father had myasthenia gravis but there Andrea C. Adams, MD ion regarding a 3-month history of subacute onset was no family history of dementia. General examina- Eoin P. Flanagan, progressive cognitive decline. She complained of tion revealed a restless woman with pseudobulbar MBBCh memory difficulties particularly with short term affect who was unable to provide a meaningful his- recall. Decision-making and organizational skills were tory. Neurologic examination revealed multiple increasingly difficult. She also developed sudden brief abnormalities. Mental status testing revealed a mild Correspondence to jerking movements of her body and progressive gait to moderate degree of encephalopathy including F. Ali: imbalance and incoordination leading to falls. Three [email protected] abnormalities in attention, frontal lobe function, months after onset, she could not work, drive, cook, and comprehension. Kokmen short test of mental or perform activities of daily living. She had not had status score was 23 out of 38 (29/38 or less consistent episodes suggestive of seizures. Her medical history with dementia). There was multifocal myoclonus and was remarkable for celiac disease diagnosed 9 years postural tremor. Cerebellar examination revealed previously, which resolved with a gluten-free diet, col- appendicular and gait ataxia. Muscle strength and lagenous colitis, Raynaud syndrome, osteopenia, anx- reflexes were normal. Sensory examination was unre- iety, and prior episodes of hyponatremia related to liable due to dementia. polydipsia. Current medications included amitripty- Question for consideration: line, venlafaxine, and Pepto-Bismol. She worked as a financial analyst, had never consumed tobacco 1. What is the differential diagnosis? GO TO SECTION 2 From the Departments of Neurology (F.A., A.C.A., E.P.F.) and Gastroenterology and Hepatology (J.A.M.), Mayo Clinic, Rochester, MN. Go to Neurology.org for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article. © 2017 American Academy of Neurology e7 ª 2017 American Academy of Neurology. Unauthorized reproduction of this article is prohibited. SECTION 2 or T2 hyperintensities in the caudate were not found) Differential diagnoses included various potential despite a high clinical suspicion given the rapidly pro- mechanisms for a rapidly progressive dementia. gressive dementia accompanied by ataxia and myoclo- nus. Similarly, imaging did not reveal changes 1. Prion disease (e.g., Creutzfeldt-Jakob disease suggestive of an autoimmune encephalopathy, such as [CJD]) mesial temporal lobe signal abnormalities. Initial labo- 2. Autoimmune/paraneoplastic encephalopathy ratory testing at an outside facility revealed a sodium 3. Toxic/metabolic encephalopathy (e.g., medication- level of 118 mmol/L (normal 135–145) a few weeks induced, electrolyte disturbance, serotonin syn- prior to our evaluation and repeat testing after fluid drome, heavy metal toxicity) restriction revealed a level of 129 mmol/L with a serum 4. Neoplasm (e.g., gliomatosis cerebri, neoplastic osmolality of 262 mOsm/kg (normal 275–295). How- meningitis, intravascular lymphoma) ever, the patient’s confusion persisted and hence her 5. Infectious etiologies (e.g., HIV, syphilis, Whipple) referral to Mayo Clinic for further evaluation. Thyroid 6. Vascular disorders (e.g., CNS vasculitis, b-amyloid- function was normal. Systemic autoimmune disease related angiitis) with nervous system involvement was also a consider- 7. Other neurodegenerative etiologies (e.g., early- ation but antinuclear, SSA/SSB, myeloperoxidase, and onset Alzheimer disease) PR-3 antibodies were all negative. Celiac disease has 8. Other systemic or extraneurologic autoimmunity been linked to ataxia and rarely dementia. Celiac serol- that can be accompanied by neurologic manifes- ogy was negative, consistent with serologic remission tations (e.g., celiac disease) from her gluten-free diet. To further evaluate nutri- Given the concomitant use of a tricyclic antidepres- tional deficiencies, particularly given the potential of 12 sant (amitriptyline) and serotonin and norepinephrine malabsorption, vitamin B ,folate,vitaminB6,and reuptake inhibitor (venlafaxine) accompanied by confu- vitamin E were all assessed and within normal limits. sion and myoclonus, serotonin syndrome was a consid- Serum levels of arsenic, mercury, cadmium, lead, mag- eration. However, there were no recent medication nesium, copper, and zinc were also normal. adjustments, no fever was present, and the presentation An abdominal X-ray performed as part of the over 3 months was felt to be too insidious. MRI brain workup for any relationship to her gastrointestinal with gadolinium contrast and magnetic resonance conditions revealed multiple radio-opaque deposits angiogram of the brain were both normal at an outside (figure, A). 18F-fluorodeoxyglucose (FDG) PET scan facility prior to referral to our institution. The normal of the brain was done to evaluate for primary neuro- imaging excluded primary brain neoplasm or metastatic degenerative disorders and showed a generalized mild lesions as the cause and made vasculitis and meningitis to moderate reduction of FDG uptake in both cere- unlikely. There were no radiologic features suggestive of bral hemispheres, consistent with a nonspecific CJD (cortical ribboning on diffusion-weighted images encephalopathy and not suggestive of Alzheimer or Figure Abdominal X-ray and brain FDG-PET findings (A) Abdominal X-ray shows speckles of scattered speckled radio-opaque deposits throughout but most prominent in the ascending and sigmoid colon (arrows). (B) FDG-PET brain shows diffuse nonspecific mildly reduced uptake consistent with metabolic encephalopathy as opposed to a specific neurodegenerative disorder (normal uptake 5 blue/black; mildly reduced uptake 5 green; moderately reduced uptake 5 yellow; markedly reduced uptake 5 red). e8 Neurology 89 July 11, 2017 ª 2017 American Academy of Neurology. Unauthorized reproduction of this article is prohibited. Lewy body disease (figure, B). EEG showed normal (normal #0.02 nmol/L). VGKCc testing in the posterior rhythm, diffuse intermittent slowing in the CSF was normal. All other neural antibodies in serum delta frequency range, but no periodic sharp waves and CSF including glutamic acid decarboxylase 65 that can occur with CJD. CSF analysis revealed a nor- autoantibodies, NMDA, AMPA, and GABA-B mal cell count, protein, and glucose; oligoclonal receptor autoantibodies, anti-neuronal nuclear auto- bands were not present and neuron-specific enolase antibodies type 1 (anti-Hu) and 2 (anti-Ri), and Pur- was normal. CSF infectious parameters were unre- kinje cell autoantibody type 1 (anti-Yo), 2, and Tr vealing and included herpes simplex virus, varicella- were all negative. zoster virus, and Whipple PCR and syphilis testing. Question for consideration: Comprehensive neural autoantibody testing in serum revealed elevated voltage-gated potassium channel 1. How could the clinical significance of the VGKCc complex (VGKCc) autoantibodies at 0.06 nmol/L autoantibody be further clarified? GO TO SECTION 3 Neurology 89 July 11, 2017 e9 ª 2017 American Academy of Neurology. Unauthorized reproduction of this article is prohibited. SECTION 3 tive VGKCc autoantibody with negative LGI1 and While the subacute encephalopathy, myoclonus, fam- Caspr2 antibody testing is of uncertain clinical ily history of autoimmunity, and hyponatremia could significance. fit anti-leucine-rich glioma inactivated-1 (LGI1) Questions for consideration: autoantibody encephalitis, VGKCc autoantibody subtyping for LGI1 and anti-contactin-associated 1. What is the diagnosis? protein-2 (Caspr2) antibodies were negative. A posi- 2. How was the diagnosis confirmed? GO TO SECTION 4 e10 Neurology 89 July 11, 2017 ª 2017 American Academy of Neurology. Unauthorized reproduction of this article is prohibited. SECTION 4 risk of bismuth absorption through the gastrointes- The patient carried a diagnosis of collagenous colitis, tinal tract due to comorbid conditions of micro- for which she took bismuth subsalicylate 1,048 mg scopic colitis and possible celiac disease. Both of daily for approximately 2 years preceding presenta- these conditions have been linked to altered muco- tion. Whole blood bismuth level at 948 ng/mL and sal permeability and conceivably increased bismuth urine bismuth level at .406.5 ng/mL were in the absorption.6 toxic range (normal ,50; toxic .200 ng/mL). The Various mechanisms of neurotoxicity have been abdominal X-ray findings were a clue suggestive of postulated primarily based on mouse model experi- bismuth accumulation in the gut. The diagnosis was ments. Bismuth has been shown to travel retrogradely bismuth neurotoxicity causing rapidly progressive through the axons to cell bodies after intramuscular dementia, myoclonus, and ataxia. The patient’s initial instillation.7 In vitro rat brain tissue experiments have hyponatremia could have resulted from secretory also shown accumulation of bismuth in astrocytes.8 diarrhea from collagenous colitis, excess water drink- Once in a nervous system cell, mechanism of injury is ing in the setting of the disinhibition, or syndrome