Major & Mild Neurocognitive Disorders (Dementia)

Introduction

Neurocognitive disorders (NCDs) represent a significant portion of the MCCQE1 objectives, particularly within the domains of Internal Medicine, Psychiatry, and Geriatrics. With Canada’s aging population, the ability to diagnose, manage, and advocate for patients with cognitive decline is a critical skill for the Canadian physician.

The DSM-5 replaced the term “Dementia” with Major Neurocognitive Disorder, and “Mild Cognitive Impairment” with Mild Neurocognitive Disorder. However, “Dementia” remains in common clinical use.

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Key Distinction for MCCQE1: The primary differentiator between Mild and Major NCD is the interference with independence in everyday activities (Activities of Daily Living - ADLs).

Mild NCD: Cognitive decline does not interfere with capacity for independence in everyday activities (though greater effort or compensatory strategies may be required).
Major NCD: Cognitive decline interferes with independence in everyday activities.

Clinical Approach and Diagnosis

The diagnosis of dementia is clinical, supported by objective cognitive testing and investigations to rule out reversible causes.

The Diagnostic Framework

Step 1: History & Collateral Information

A reliable history is often impossible to obtain solely from the patient. Collateral history from a family member or caregiver is essential.

Onset: Gradual (Alzheimer’s) vs. Step-wise (Vascular) vs. Rapid (CJD).
Course: Progressive, fluctuating, or stable?
Functional Status: Impact on Instrumental ADLs (banking, shopping, driving) and Basic ADLs (bathing, dressing).
Safety: Driving, stove use, wandering, firearms.

Step 2: Cognitive Screening

Use validated tools. In Canada, the Montreal Cognitive Assessment (MoCA) is widely preferred over the MMSE for detecting Mild NCD due to its higher sensitivity to executive dysfunction.

MoCA: Scores < 26/30 generally indicate impairment (add +1 point for education ≤ 12 years).
MMSE: Scores < 24/30 generally indicate impairment.

Step 3: Physical & Neurological Exam

Vitals: Orthostatic hypotension?
Neurological: Focal signs (Vascular), Parkinsonism (Lewy Body), Gait abnormalities (NPH), Primitive reflexes.
General: Signs of hypothyroidism, B12 deficiency signs (neuropathy).

Step 4: Investigations (Rule out Reversible Causes)

Apply Choosing Wisely Canada recommendations. Do not order imaging for uncomplicated headache or simple syncope, but neuroimaging is recommended for new cognitive decline.

Standard Canadian Workup:

Labs: CBC, Electrolytes, Calcium, Glucose, TSH, Vitamin B12.
Imaging: CT Head or MRI Brain (to rule out stroke, tumor, subdural hematoma, NPH).
Optional (based on clinical suspicion): Syphilis serology, HIV, heavy metals, LP (if rapid progression/infection suspected).

Reversible Causes Mnemonic

Mnemonic: DEMENTIA

Drugs (Anticholinergics, Benzodiazepines, Opioids)
Emotional (Depression - “Pseudodementia”)
Metabolic (Hypothyroidism, Hypercalcemia, B12 deficiency)
Eyes/Ears (Sensory deficits can mimic cognitive decline)
Normal Pressure Hydrocephalus (NPH)
Tumor / Trauma (Subdural hematoma)
Infection (Syphilis, HIV, UTI/Delirium)
Anemia / Alcohol (Wernicke-Korsakoff)

Specific Neurocognitive Disorders

Understanding the nuances between different types of dementia is high-yield for MCCQE1.

Alzheimer’s Disease

Epidemiology: Most common cause (60-80%).

Pathophysiology: Amyloid plaques and neurofibrillary tangles (tau protein); cholinergic deficiency.

Clinical Features:

Insidious onset, gradual progression.
Early memory loss (anterograde amnesia).
Visuospatial deficits (getting lost).
Language deficits (word-finding difficulties).
Late: Apraxia, agnosia.

Comparison of Features

Feature	Alzheimer’s	Vascular	Lewy Body	Frontotemporal
Onset	Gradual	Sudden or Step-wise	Gradual	Gradual (< 65 yo)
Primary Deficit	Memory (Episodic)	Executive Function / Speed	Attention / Visuospatial	Behavior / Language
Motor Signs	Late	Early (Focal)	Early (Parkinsonism)	Rare (unless ALS overlap)
Imaging	Hippocampal atrophy	Infarcts / White matter change	Minimal atrophy	Frontal/Temporal atrophy

Management Guidelines

Management in the Canadian context involves a multidisciplinary approach (CanMEDS: Collaborator).

1. Non-Pharmacologic Management (First Line)

Education & Support: Alzheimer Society of Canada referral.
Safety: MedicAlert® Safely Home program.
Behavioral Management: Identify triggers for BPSD (Behavioral and Psychological Symptoms of Dementia). Use the “P.I.E.C.E.S.” model (Physical, Intellectual, Emotional, Capabilities, Environment, Social).
Advance Care Planning: Establish Goals of Care early.

2. Pharmacologic Management

Based on the 5th Canadian Consensus Conference on the Diagnosis and Treatment of Dementia (CCCDTD5).

Cognitive Enhancers

Indicated for Alzheimer’s, Lewy Body, and Parkinson’s Dementia. (Mixed evidence for Vascular; Not indicated for FTD).

Cholinesterase Inhibitors (ChEIs): Donepezil, Rivastigmine, Galantamine.
- Side Effects: Nausea, diarrhea, bradycardia, syncope, insomnia/vivid dreams.
- Contraindications: Active PUD, conduction abnormalities (LBBB, heart block).
NMDA Receptor Antagonist: Memantine.
- Used for moderate-to-severe AD, often added to ChEIs.

Management of BPSD (Agitation/Aggression)

First line: Non-pharm (music, massage, distraction).
Pharmacologic: Reserve for severe distress or risk of harm.
- SSRIs (Citalopram/Sertraline) for agitation/anxiety.
- Atypical Antipsychotics (Risperidone, Olanzapine, Quetiapine) – Use with caution.
- Black Box Warning: Increased risk of mortality (stroke/cardiac) in elderly patients with dementia-related psychosis.

3. Legal and Ethical Considerations (Canadian Context)

Driving:
- Physicians have a duty to report unfit drivers.
- Laws vary by province (Mandatory reporting in ON, MB, SK, NL, NT, YT; Discretionary in others, but generally ethical duty overrides).
- Mild NCD: May require on-road testing.
- Major NCD (Moderate/Severe): Unfit to drive.
Power of Attorney (POA): Encourage patients to designate a Substitute Decision Maker (SDM) for Personal Care and Property while they still have capacity.
Capacity: Competency is legal; Capacity is clinical. Capacity is task-specific (e.g., capacity to manage finances vs. capacity to consent to surgery).

Key Points to Remember for MCCQE1

Depression vs. Dementia: In elderly patients, depression can present as “pseudodementia” (subjective memory complaints, “I don’t know” answers). Treat the depression first.
Delirium vs. Dementia: Delirium is acute, fluctuating, and affects attention. Dementia is chronic and affects memory. Delirium is a medical emergency.
NPH Triad: “Wet, Wobbly, Wacky” (Incontinence, Gait disturbance, Dementia). Treatable with shunting.
Rapidly Progressive Dementia: Think CJD (myoclonus, 14-3-3 protein) or Autoimmune Encephalitis.
Canadian Screening: The MoCA is the standard, developed in Canada.

Sample Question

Case Presentation

A 76-year-old male is brought to the clinic by his wife due to concerns about his cognition. She reports that over the past year, he has been seeing “little children” in their backyard who are not there. His cognition seems to fluctuate significantly; some days he is alert and interacts normally, while other days he is drowsy and confused. On physical examination, he exhibits cogwheel rigidity in the upper extremities and a shuffling gait. He has no history of stroke.

Which one of the following medications should be avoided in the management of this patient’s symptoms?

Options

Explanation

The correct answer is:

C. Haloperidol

Detailed Explanation: The clinical presentation is classic for Dementia with Lewy Bodies (DLB). The core features include fluctuating cognition, recurrent detailed visual hallucinations, and spontaneous features of parkinsonism.

C is correct: Patients with DLB have a severe neuroleptic sensitivity. Administration of typical antipsychotics (like Haloperidol) can precipitate irreversible parkinsonism, severe sedation, neuroleptic malignant syndrome, and even death. They are contraindicated.
A is incorrect: Cholinesterase inhibitors (like Rivastigmine) are the first-line treatment for cognitive and behavioral symptoms in DLB.
B is incorrect: Levodopa may be used to treat the parkinsonism symptoms, although the response is often less robust than in idiopathic Parkinson’s disease.
D is incorrect: Memantine can be used in DLB, though evidence is stronger for Alzheimer’s.
E is incorrect: Melatonin is often used to manage REM sleep behavior disorder associated with DLB.

Canadian Guidelines

CCCDTD5 (5th Canadian Consensus Conference on the Diagnosis and Treatment of Dementia): Provides the framework for investigation and management.
Choosing Wisely Canada: Geriatrics and Radiology recommendations regarding neuroimaging and antipsychotic use in the elderly.
Canadian Task Force on Preventive Health Care: Guidelines on screening for cognitive impairment (generally recommends against screening asymptomatic older adults, but supports investigating those with concerns).

References

Gauthier S, et al. Fourth Canadian Consensus Conference on the Diagnosis and Treatment of Dementia. Can J Neurol Sci. 2014. Link (Note: 5th Consensus updates incorporated where available).
Ismail Z, et al. Canadian Consensus Conference on the Diagnosis and Treatment of Dementia (CCCDTD5). Alzheimer’s & Dementia. 2020.
Choosing Wisely Canada. Geriatrics: Antipsychotics. Link
Nasreddine ZS, et al. The Montreal Cognitive Assessment, MoCA: a brief screening tool for mild cognitive impairment. J Am Geriatr Soc. 2005.
Medical Council of Canada. MCCQE Part I Objectives: Neurocognitive Disorders. Link