Neurologic Differential Diagnosis

Question 1

Framework for neurological DDx

Answer 1

• Based on the patient history, results of the neurological exam, & localization of anatomy to identify patient problems
• Determine if appropriate to treat
• Determine hypothesis generation related to movement related dysfunction

Question 2

Step 1 of neurological DDx framework

Answer 2

• Elicition of clinical facts derived from patient Hx & neurologic exam
• Signs & Sx are interpreted in the context of the relevant anatomy & physiology
• Goal is to generate a list of hypothesized lesion localizations that direct evaluation & special testing selection
• Hx & neurologic evaluation results are interpreted & s/s are clustered into recognizable syndromes

Question 3

Step 2 of neurological DDx framework

Answer 3

• Localization of the lesion to determine an anatomical Dx
• Identification of the part(s) of the nervous system that could most likely account for the complete patient presentation

Question 4

Step 3 of neurological DDx framework

Answer 4

• Anatomic Dx is combined with the temporal features of the disease: mode of onset, course of illness, relevant past medical & family Hx, lab findings
• Establish a timeline

Question 5

Describe a hypothetico-deductive reasoning strategy

Answer 5

• Generation & verification of hypothesis are confirmed or negated on an ongoing basis as patient information & data is collected

Question 6

Elicitation of clinical facts: Observation, Medical record, & Subjective

Answer 6

• PMH and family history: risk factors
• Drug history: antipsychotics, anti epileptics, benzodiazepines, statins, lithium, methotrexate, opioids
• History of present illness (HPI): temporal factors
• Imaging or other studies
• Labs: antibody testing, lumbar puncture, B12 & folate levels, inflammatory markers (ESR & C-reactive protein), liver function tests, thyroid tests, complete blood count & basic metabolic panel, hemoglobin A1C & heavy metal screening

Question 7

Emergency situations/immediate medical assistance required

Answer 7

• Loss of consciousness or difficulty to arouse
• Extreme confusion non consistent with premorbid status
• Uncontrolled seizure activity
• Acute infection with neurological signs (nuchal rigidity, intense localized back pain)
• Rapid onset of focal neurological deficits suggesting stroke (BE FAST)
• Spinal column instability
• Nonresponsive autonomic dysreflexia

Question 8

Urgent situations/referral required

Answer 8

• Acute onset of neurologic signs such as incontinence, saddle paresthesia, abnormal reflexes
• Progressive neurologic signs in known neurologic diagnosis that is not degenerative
• Evidence of motor neuron disease: Fasciculation, atrophy, weakness in limbs or trunk not previously diagnosed
• Change in autonomic status
• Bulbar and other cranial nerve signs/symptoms (except acute onset)
• Constant headache that worsens over time
• TIA symptoms
• Vertebral artery insufficiency
• Neuro signs inconsistent with diagnosis
• Signs/symptoms of systemic illness
• Significant changes in personality or cognitive status

Question 9

Patient signs/neurological considerations

Answer 9

• Mental status
• Cranial nerve function
• Force production
• DTR/pathological reflexes
• Coordination
• Gait
• Sensory integrity

Question 10

Describe cognition neurological signs

Answer 10

• Memory: medial temporal lobes, hippocampus, amygdala
• Language: dominant hemisphere (usually L)
• Expressive aphasia: Broca’s area (frontal lobe)
• Receptive aphasia: Wernicke’s area (temporal lobe)
• Attention: frontal lobe
• Perseveration: frontal lobe
• Impulsivity: frontal lobe
• Apraxia

Question 11

Brain structures and functions

Answer 11

• Frontal lobe (Broca’s area): initiation, judgement, memory, impulse control, sequencing, social behavior
• Parietal lobe: sensory integration, awareness of body image & environment
• Temporal lobe (Wernicke’s area): long term memory, auditory processing
• Occipital lobe: visual field, color discrimination
• Cerebral cortex: Motor cortex/motor homunculus = contralateral control of movement; Somatosensory cortex/sensory homunculus = contralateral perception of sensation; Visual cortex = contralateral perception of vision; Auditory cortex = bilateral reception of auditory input
• Corpus callosum: facilitates communication between the right & left hemispheres of the brain

Question 12

List the cortical functions

Answer 12

• Cognition
• Memory
• Apraxia
• Aphasia
• Agnosia

Question 13

Slide 15

Question 14

Coordination deficits testing

Answer 14

• Test joint position sense first (eyes open then closed)
• If joint position sense is adequate test coordination: heel to shin, finger to nose, repeated movements
• Unilateral: ipsilateral cerebellar syndrome
• Bilateral: bilateral cerebellar syndrome
• Truncal ataxia, gait ataxia, without limb incoordination = midline cerebellar syndrome

Question 15

Slide 17

Question 16

Timing/temporal factors

Answer 16

• Establish a timeline
• Review the timeline & note the following: abrupt or insidious onset, episodic or continuous presentation, exacerbation or remission, stable or progressive improvement/regression, age of onset

Question 17

Lab tests specific to neurological DDx

Answer 17

• Lumbar puncture: analysis of cerebrospinal fluid (CSF), assists with Dx MS, Guillain-Barré syndrome, normal pressure hydrocephalus, meningitis, encephalitis
• Electrophysiological studies: assists with Dx ALS, spinal muscular atrophy, peripheral neuropathy, myasthenia, graves, myopathy, brachial plexopathy
• Imaging: CT, MRI, PET, angiography
• Biopsies: brain, muscle, nerve, artery
• Standard laboratory analysis discussed on slide 7

Question 18

Localization of findings

Answer 18

• CNS vs PNS
• UMN vs LMN
• Specific location: basal ganglia (BG), cerebellum, cranial nerves, cognitive signs/symptoms (cognition, memory, apraxia, aphasia, agnosia), autonomic dysfunction

Question 19

Define agnosia and aphasia

Answer 19

• Agnosia: inability to interpret sensations & hence recognize things
• Aphasia: Wernicke’s area (L temporal lobe, comprehension) and Broca’s area (L frontal lobe, production)

Question 20

CNS vs PNS localization of weakness

Answer 20

• PNS: spinal nerves, brachial plexus, peripheral nerves, lumbosacral plexus, cauda equina, conus medullaris, facial nerve (CN VII)
• CNS: region of motor homunculus, primary motor cortex, descending motor pathways, brainstem, cervical spinal cord

Question 21

Localization of stiffness

Answer 21

• Spasticity: descending motor pathways at the cortical brainstem, or spinal cord levels
• Rigidity: basal ganglia
• Hypertonicity: descending motor pathways especially the reticulospinal & corticospinal tracts
• Hypotonicity: cerebellum, descending motor pathways, & spinal cord in the acute stage of injury

Question 22

Localization of sensory abnormality like joint position/vibration/fine discriminative touch and pain/temperature/crude touch

Answer 22

• Joint position/vibration/fine discriminative touch: PNS = sensory receptors, ascending peripheral nerves, spinal nerves, trigeminal nerve; CNS = dorsal column medical lemniscus of spinal cord, brainstem, thalamus, primary somatosensory cortex
• Pain/temperature/crude touch: PNS = sensory receptors, ascending peripheral nerves, spinal nerves, trigeminal nerve; CNS = anterolateral pathway of spinal cord, brainstem, thalamus, primary somatosensory cortex

Question 23

UMN versus LMN signs

Answer 23

• UMN: weakness, NO atrophy except in chronic disuse, NO fasciculations, increased reflexes except in acute lesions, & increased tone except in acute lesions
• LMN: weakness, atrophy, fasciculations, decreased reflexes, & decreased tone

Question 24

Patterns of weakness based on location of lesion

Answer 24

• Cortex: contralateral face & body
• Brainstem: ipsilateral face & contralateral body
• SCI: level of the lesion or below
• Root lesion: dermatomal/myotome pattern of the root
• Polyneuropathy: distal loss greater than proximal loss
• NMJ: patchy, decreased grip strength/endurance, face symptoms can be common
• Myopathy: proximal loss greater than distal loss

Question 25

Central causes of sensory loss

Answer 25

• Relate the lesion site to sensory distribution (homunculus)
• Loss of certain modalities (pain/temp, vibration, light touch)
• Loss of higher level perceptual functions: stereognosis, graphesthesia, extinction

Question 26

Peripheral causes of sensory loss

Answer 26

• Peripheral nerve distribution (ex: LFCN)
• Dermatome (spinal nerve root level)
• Stocking glove (polyneuropathy, DM II)

Question 27

Cerebellum signs and symptoms

Answer 27

• Dysmetria, DDK, hyper or hypometria
• Nystagmus
• Dysarthria
• Ataxia
• Difficulty with motor planning & learning

Question 28

Basal ganglia signs and symptoms

Answer 28

• Bradykinesia
• Hypokinesia
• Athetosis/chorea
• Tremor
• Dystonia

Question 29

Brainstem signs and symptoms

Answer 29

• Cardiorespiratory funciton
• Provides sensory & motor innervation to face & neck
• Passageway for ascending sensory tracts & descending motor pathways
• Regulation of consciousness
• Sleep/wake cycle
• Autonomic control

Question 30

Spinal cord signs and symptoms

Answer 30

• Bowel/bladder dysfunciton
• Sexual funciton
• Complete
• Incomplete: anterior cord, central cord, Brown sequared

Question 31

What is the 3 step process

Answer 31

• Step 1: patient history and neurological examination
• Step 2: Localization of lesion that is based on the clinical findings
• Step 3: Combining anatomic diagnosis with temporal features, timeline, and ongoing verification & refinement of hypotheses