Approach to Cognitive Impairment

This section is divided into 3 parts:

  1. Different approaches to cognitive impairment
  2. Causes of dementia
  3. Assessment of cognitive function


Different approaches to assessing cognitive complaints:

The approach to cognitive complaints begins with the clinical assessment. This starts with the history and physical examination.  There are many ways of approaching patients with dementia or those suspected to have cognitive problems.  We will outline these approaches below.  These approaches are used together in assessing the individual patient. Each of the approaches highlights one of the aspects of cognitive neurological disorders, and may be used to evaluate the presence and type of dementia.

For example, approaching the patients based on the severity of cognitive impairments allows classification of patients as having nonspecific cooperative complaints, mild cognitive impairments or dementia. Patients with dementia will have impairment of their activities of daily living.  Patients with mild cognitive impairment will have findings on the cognitive examination without impairments of activities of daily living.  Patients who have nonspecific cognitive complaints generally have no impairment of activities of daily living and a normal or near normal cognitive examination. Often these patients have secondary conditions that are causing the cognitive complaints such as sleep deprivation, anxiety, depression or medication use.

Another approach is to determine which cognitive domain was the first to be affected. For example in Alzheimer’s disease memory impairment usually precedes deterioration in activities of daily living or impairment in other cognitive domains. In primary progressive aphasia, language is impaired in the initial stages. If executive function is impaired before language or memory, then think of the “subcortical” dementias such as vascular dementia, diffuse Lewy body disease. In patients with early visuospatial deficits, think of Alzheimer’s disease in particular the “posterior cortical atrophy” variant. On occasion, you will be presented with patients who are in advanced or late stages of dementia. They are often akinentic and mute. It is often worth-while to try to find out which cognitive domain was the first to be affected to determine etiology in patients presenting late.

Non-cogntive features allow us another way of approaching dementias. Determine whether there is a movement disorder as part of the disease process. Certain dementias like diffuse Lewy body disease, progressive supranuclear palsy and multisystem  atrophy have cognitive deterioation accompanied by a movement disorder. Assess the patient for bradykinesia, rigidity, spasticity, abnormalities in gait and cerebellar function. Other dementias, such as, Alzheimer’s disease and Fronto-temporal dementia are rarely accompanied by a movement disorder.

Please see the list below that outlines the different approaches.

1. By severity:
Activities of daily living (ADLS): are the ADLS affected?

  • If yes, then the progressive cognitive impairment is likely dementia.
  • If not affected, then the cognitive impairment may represent: non-specific cognitive complaints, MCI mild cognitive impairment (amnestic vs. non-amnestic) or dementia mimic (depression, etc)

2. Which is the first cognitive domain affected:

3. Is it with or without a movement disorder?
Dementia Without movement disorder:

Dementia with movement disorder:

4. Speed of onset:
Gradual onset dementia:

Rapidly progressive dementia (a.k.a. subacute encephalopathy):



Causes of dementia: (including rapidly progressive dementia/subacute encephalopathy, & many more)

1. Dementia with other disease – medical & laboratory evidence:

  • Endocrine/nutritional:
    • Hypothyroidism
    • Thiamine deficiency
    • Vitamin B12 deficiency
    • Nicotinic acid deficiency a.k.a. pellagra
  • Infection:
  • Drug intoxication:
    • Alcoholism
    • Medications
    • Heavy metal intoxication
  • Vasculitis
  • Paraneoplastic

2. Dementia alone:

3. Dementia with other neurological signs (non-cognitive signs often present):

4. Dementia with other neurologic signs (non-cognitive signs always present):



The cognitive assessment i.e. assessing higher cortical functions:

Also, included in this section is an outline to bedside cognitive assessment. Please note that other cognitive assessment tools such as the Montreal Cognitive Assessment (MoCA) and the Mini mental state examination (MMSE) are also very useful tests. I use the MMSE in patients who already have impairment of activities of daily living and the MoCA in patients who have intact activities of daily living, but there are many other ways to incorporate these tests into your practice.

What signs/symptoms does each lobe present with?

Cerebral lesions, focal:

  • Frontal lobe:
    • Apathy & abulia
    • Akinesia
    • Mood disturbance & disinhibition
    • Perseveration
    • Distractibility
    • Expressive dysphasia
    • Incontinence
    • Positive ‘primitive’ reflexes
    • Utilisation behaviour
    • Upper motor neuron (UMN) lesions
  • Parietal lobe:
    • Sensory deficits
    • Astereognosis (tactile agnosia)
    • Agraphaesthesia
    • Prosopagnosia
    • Spatial neglect (more on non-dominant, right angular gyrus “egocentric neglect”, patient makes errors with objects to the left of himself)
    • Sensory inattention:
      • Autopagnosia: can’t identify body parts
    • Lower homonymous quadrantanopia (lower visual field)
    • Visual agnosia (parieto-occipital lobe)
    • Auditory agnosia (voices, music, telephone)
    • Dominant:
      • Acalculia
      • Agraphia
      • Left-right agnosia/disorientation
      • Finger agnosia
      • Gerstmann’s syndrome (impairment of the above Dominant parietal lobe functions +Alexia ‘inability to read’)
    • Non-dominant:
      • Dressing apraxia
      • Constructional apraxia (can’t make shapes or patterns)
      • Anosognosia (lack of awareness that limbs are impaired)
    • Topographic apraxia (e.g. can’t find their way back to bed)
    • Occipital lobe:
      • Cortical blindness
      • Visual agnosia (parieto-occipital lobe)
      • Impaired colour perception
      • Impaired movement perception
    • Temporal lobe:
      • Memory impairment
      • Receptive dysphasia
      • Auditory agnosia
      • Cortical deafness
      • Upper homonymous quadrantanopia (upper visual field)
      • A type of Spatial neglect (more on non-dominant, superior temporal gyrus “allocentric neglect” patient makes errors with objects to the left of his visual field)


How to examine each lobe:


  • Time, Place & person
  • Mini mental state examination (MMSE) may be indicated


  • Also see section on approach to abnormal speech
  • Determine the following:
    • Fluency
    • Comprehension
    • Naming
    • Repetition
    • Articulation
    • Phonation
    • Reading
    • Writing

Frontal lobe:

  • Primitive reflexes:
    • Utilisation behaviour: present the patient with objects e.g. bottle of water & a cup, an envelope & a sheet of paper, they use it without being told to.
    • Palmomental reflex: scratch the thenar eminence in a proximal to distal direction, ipsilateral chin & perioral muscle contraction
    • Grasp reflex: stroke the patient’s hand & when they close it pull to stretch the tendons, the patient grasps & doesn’t let go
    • Snout reflex: touch the nasal philtrum, the lips protrude (NB. This isn’t the pout reflex which is sign of UMN lesion & is stimulated by touching the lips)
    • Sucking reflex: touch the lips (or place an objects), sucking movements occur
    • Rooting reflex: stroke the cheek near the mouth, the lips move towards the stimulus
    • Glabella tap (glabellar reflex): tap the forehead repeatedly, persistent blinking (Myerson’s sign, not sensitive or specific)
  • Fundoscope:
    • Optic atrophy, papilloedema
    • Foster Kennedy syndrome: ipsilateral optic atrophy, contralateral papilloedema
  • Anosmia
  • Gait apraxia (bifrontal, or diffuse disease)
  • Test Judgement:
    • “what would you do if you found a letter on the sidewalk?”
  • Test for Concrete thinking (a.k.a. impairment of abstraction), Ask the patient to interpret a proverb:
    • “a stitch in time saves nine”
    • “a rolling stone gathers no moss”

Parietal Lobe:

  • General:
    • Test sensation:
      • Test light touch & pain
      • Test vibration & proprioception
      • Test two point discrimination
    • Astereognosis (tactile agnosia):
      • Place an object in their hand with their eyes closed e.g. a key
    • Test for agraphaesthesia:
      • Stroke out numbers on the palm of their hand with eyes closed
    • Spatial neglect (more on non-dominant):
      • Draw a clock face with the numbers
  • Non-dominant:
    • Ask them to copy out different patterns (Constructional apraxia)
    • Dressing apraxia
  • Dominant:
    • Finger agnosia:
      • Ask them to close their eyes & tell you which finger has been touched
    • Ask them to count fingers (acalcula)
    • Test for agraphia (ask them to write)
    • Test for Left-right agnosia/disorientation:
    • “show me your right hand”
    • “touch your right ear with your left hand”
  • Visual fields:
    • Lower quadrantic hemianopia

Occipital lobe:

  • Test for Alexia
  • Test visual fields:
    • Homonymous hemianopia

Temporal lobe:

  • Memory: test immediate recall, recent memory and remote memory
  • Visual fields:
    • Upper quadrantic hemianopia

Mini-mental status examination (MMSE) Score & Interpretation:
MMSE score:

  • Score <24 should lead to a more detailed examination investigation
  • Score of 21 suggests mild dementia syndrome
  • Score <15 or <10, indicates severe dementia
  • If MMSE is >24, the patient may still have mild cognitive impairment, so use more sensitive scales such as Montreal Cognitive Assessment (MoCA)
  • If ADLS are not impaired use more sensitive scales such as Montreal Cognitive Assessment (MoCA)

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