Basic Principles of Clinical Diagnosis

Question 1

What are the four major etiologies of neurological disorder?

Answer 1

• extrinsic, systemic, vascular, and intrinsic

Question 2

What are extrinsic disorders? How do they lead to neurological dysfunction? Give some general examples.

Answer 2

• these lead to compression of the underlying/adjacent structures
• these are usually surgically removable
• brain: blood clots (hematomas), abscess, tumor, hydrocephalus
• spinal cord: spondylosis, prolapsed disc, tumor, syringomyelia (expansion of central canal into a syrinx)
• cranial nerves: tumor, aneurysm
• spinal nerve roots: tumor, prolapsed disc

Question 3

What are systemic disorders? How do they lead to neurological dysfunction? Give some general examples.

Answer 3

• these result in neurological dysfunction due to metabolic, toxic, and nutritive abnormalities
• intoxication, dietary deficiency, cardiovascular failure, liver failure, kidney failure, diabetes, etc.

Question 4

What are vascular disorders? How do they lead to neurological dysfunction? Give some general examples.

Answer 4

• these damage the circulation to the nervous system
• a stroke is a rapid development of a vascular lesion
• occlusion (via thromboembolism), infarction, hemorrhage (bleeding into the nervous tissue)

Question 5

What are intrinsic disorders? How do they lead to neurological dysfunction? Give some general examples.

Answer 5

• these are usually more rare, chronic, and irreversible
• these are primary disorders of the nervous system
• neoplasm, inflammation, degenerative diseases

Question 6

What is meant by “dissociative sensory loss?”

Answer 6

• this means a patient has lost his sense of fine touch, proprioception, and vibration, but with preservation of crude touch, pain, and temperature (or vice versa)
• unilateral lesions in the dorsal column result in ipsilateral loss of proprioception (because these decussate in the pyramids)
• unilateral lesions in the spinothalamic tracts result in contralateral loss of pain/temp (because these decussate in the spinal cord)

Question 7

Lesions of Lower Motor Neurons

Answer 7

• these will affect the ipsilateral side

- weakness (paresis), wasting, hyporeflexia, hypotonia, fasciculations, flaccid paralysis

Question 8

Lesions of Upper Motor Neurons

Answer 8

• these can affect the ipsilateral or contralateral side, depending on where they are damaged
• weakness (paresis), hyperreflexia, hypertonia, spastic paralysis, Babinksi positive

Question 9

Lesions to the Cerebellum

Answer 9

• result in ipsilateral incoordination of eye movement (nystagmus), speech (dysarthria), upper limbs (intention tremor), and gait (ataxia)
• WITHOUT weakness and loss of sensation

Question 10

Lesions to the Basal Ganglia

Answer 10

• result in motor abnormalties (bradykinesia, rigidity, and tremor) WITHOUT loss of power, sensation, or coordination

Question 11

What’s the difference between rigidity and spasticity?

Answer 11

• rigidity is increased tone and is present throughout passive movement
• spasticity is the initial resistance to passive movement

Question 12

What are the major investigations used for neurological diagnosis?

Answer 12

• CSF analysis via lumbar puncture
• neuroimaging (x-ray for skull and vertebrae, angiography for vessels, MRI or CT for brain and spinal cord, SPECT and PET for functional imaging)
• neurophysiology (electroencephalography/EEG for electrical activity of CNS, nerve conduction studies/NCS and electromyography/EMG for PNS)
• biopsy of nerve, brain, or muscle tissues

Question 13

What are common sites of brain lesions? What does each result in?

Answer 13

• amygdala: hyperorality, hypersexuality, disinhibited behavior
• frontal lobe: dementia
• right parietal-temporal cortex: spatial neglect (agnosia of contralateral world)
• left parietal-temporal cortex: agraphia, acalculia, left-right disorientation
• reticular activating system (midbrain): coma
• mamillary bodies: Wernicke-Korsakoff
• basal ganglia: movement disorders (PD, HD)
• cerebellar hemisphere: intention tremor, limb ataxia, loss of balance
• cerebellar vermis: truncal ataxia, dysarthria
• subthalamic nucleus: (contralateral) hemiballismus
• hippocampus: anterograde amnesia (can’t make new memories)
• frontal eye field: eyes look toward the side of the lesion

Question 14

What is Brown-Sequard syndrome? Explain the clinical findings.

Answer 14

• this is hemisection of the spinal cord:
• ipsilateral UMN signs below the level of the lesion (because of corticospinal tract damage)
• ipsilateral loss of tactile, vibration, proprioception starting at 1-2 levels below the lesion (because of dorsal column damage)
• contralateral loss of pain and temperature below the level of the lesion (because of spinothalamic tract damage)
• ipsilateral loss of all sensation at the level of the lesion
• ipsilateral LMN signs at the level of the lesion
• (Horner syndrome if lesion is above T1)