Approach to the Patient with Neurologic Disease¶

Chapter 433 | Part 13: Neurologic Disorders · Part 13 – Neurologic Disorders · Chapter 433

Key Clinical Points¶

Neurologic disorders affect nearly one in three individuals and are the leading cause of disability and second leading cause of death worldwide.
The 'Neurologic Method' prioritizes defining anatomy and pathophysiology before establishing a specific diagnosis.
Rapid onset (seconds/minutes) typically indicates a vascular event, seizure, or migraine.
Symptoms worsening with heat or exercise suggest conduction block in demyelinated axons (e.g., MS).
Lhermitte syndrome (electric shock-like sensations on neck flexion) indicates demyelination in the cervical spinal cord.
Fortification spectra (slowly advancing visual scotoma with luminous edges) indicate spreading cortical depression, typically in migraine.
Anatomic localization narrows the list of possibilities and guides specific laboratory/imaging selection.
The MMSE is ~85% sensitive and specific for moderate or severe dementia in educated patients.
The Babinski sign has limited reliability for identifying upper motor neuron weakness; tests of tone, strength, and coordination are more useful.
Pyramidal tract involvement: unilateral or bilateral weakness of upper limb extensors and lower limb flexors.
Bilateral proximal weakness suggests myopathy; bilateral distal weakness suggests peripheral neuropathy.
Systemic diseases (diabetes, hypertension, lipids) are major risk factors for cerebrovascular disease.

DEFINITION & OVERVIEW¶

• Prevalence: Neurologic disorders affect nearly one in three individuals. • Global Impact: Leading cause of disability; second leading cause of death worldwide. • Trends: Cases have increased significantly over the last 30 years, expected to double by 2050 due to aging population, growth, and metabolic risk factors. • The Neurologic Method: A systematic approach to ensure technology is used judiciously and diagnosis is reached efficiently. 1. Define Anatomy → Identify the specific region (Cerebrum, Brainstem, Spinal Cord, etc.) or system (CNS vs. PNS). 2. Identify Pathophysiology → Determine if the process is metabolic, degenerative, infectious, inflammatory, or vascular. 3. Establish Diagnosis → Only after localization and pathophysiology are determined.

The Neurologic Method (Detailed)¶

• Anatomic Localization: Determine if the disorder is: - Single location vs. Multiferal vs. Diffuse. - CNS (Cerebral cortex, basal ganglia, brainstem, cerebellum, spinal cord) or PNS (peripheral nerves, neuromuscular junction, muscle). - Systemic illness context vs. isolated neurologic system involvement. • Pathophysiology Clues: - Gray matter (primary neuronal) → early cognitive disturbances, movement disorders, or seizures. - White matter (connecting pathways) → 'long tract' motor, sensory, visual, and/or cerebellar manifestations. - Progressive & Symmetric → Metabolic or degenerative origin; usually not sharply circumscribed. - Clinical Pearl: Symptoms worsening with heat or exercise suggest conduction block in demyelinated axons (e.g., MS). - Example: Paraparesis with a clear spinal cord sensory level → unlikely to be vitamin B deficiency.

EPIDEMIOLOGY¶

• Global Burden: - Impact measured in DALYs (disability-adjusted life-years) and deaths. - Significant growth in prevalence over 30 years. - Key conditions include Stroke, Alzheimer's disease, Migraine, Meningitis, Encephalitis, Parkinson's disease, Multiple sclerosis, Motor neuron diseases, Tetanus, Brain/CNS cancer, Traumatic brain injury, Spinal cord injury, and Idiopathic epilepsy.

ETIOLOGY & PATHOPHYSIOLOGY¶

• Anatomic Localization Logic: - Focus on location first to avoid missing treatable conditions (e.g., identifying 'brainstem' or 'pons' rather than immediately jumping to 'multiple sclerosis'). - Example: Visual blurring + spastic ataxic paraparesis → suggests optic nerve and spinal cord disease (MS, CNS syphilis, or vitamin B deficiency). • Pathophysiology Clues in History: - Rapid onset (seconds/minutes): Vascular event, seizure, or migraine. - Slower temporal march + headache/nausea/visual disturbance: Migraine. - Less well-localized, persistent for seconds/minutes/hours: Transient ischemic attack (TIA). - 'Positive' symptoms (tingling, involuntary movements): Suggests seizure. - 'Negative' symptoms (transient loss of function): Suggests TIA. - Stuttering onset (appear → stabilize → progress over hours/days): Cerebrovascular disease. - Remission/regression: More likely due to multiple ischemia rather than hemorrhage. - Gradual evolution (hours/days): Toxic, metabolic, infectious, or inflammatory. - Systemic signs (fever, stiff neck, altered consciousness): Infectious process. - Relapsing and remitting: MS or other inflammatory processes. - Slowly progressive without remissions: Neurodegenerative, chronic infection, gradual intoxication, or neoplasm.

CLINICAL FEATURES¶

• The Neurologic History: - Temporal Course: Determines the likely underlying pathology (e.g., rapid vs. gradual). - Patient Descriptions: Clarify ambiguous terms. - 'Dizziness' → syncope, disequilibrium, or spinning vertigo. - 'Numbness' → loss of feeling, tingling (positive), or weakness. - 'Blurred vision' → unilateral visual loss or diplopia. - Corroboration: Essential for patients with memory loss, aphasia, lack of insight, or intoxication; critical for events involving loss of consciousness. - Family History: - Mendelian disorders (e.g., Huntington's, Charcot-Marie-Tooth). - Polygenic conditions (e.g., MS, migraine, epilepsy). - Systemic links (e.g., hypertension/heart disease in stroke patients; multisystem markers like neurofibromatosis or Wilson's disease). - Medical Illnesses: - Metabolic/Systemic: Diabetes, hypertension, lipids → cerebrovascular risk. - Specific associations: Valvular heart disease (abscess), coagulopathy (hemorrhage), AIDS (toxoplasmosis/lymphoma), Marfan's (dissection/aneurysm). - Drug & Toxin Exposure: - Sedatives/Antidepressants → acute confusion in elderly. - Aminoglycosides → muscle weakness (myasthenia gravis) or ototoxicity (dizziness). - Vincristine → peripheral neuropathy. - Cyclosporine → encephalopathy. - Immunotherapies (Checkpoint inhibitors/CAR T cells) → brain edema, inflammation, demyelination. - Vitamin A → intracranial hypertension ('pseudotumor cerebri'). - Pyridoxine → peripheral neuropathy. - Alcohol: Most prevalent neurotoxin. - Formulating Impression: Assess communication, anxiety, depression, and cognitive status immediately upon entry.

DIFFERENTIAL DIAGNOSIS¶

• Anatomic Localization Strategy: - Use history/exam to determine location → narrows possibilities → selects specific tests. - Integration of localization, onset, medical data, and lab findings leads to etiological diagnosis.

Table 433-1: Findings for Localization¶

• Cerebrum: - Abnormal mental status or cognitive impairment. - Seizures. - Unilateral weakness and sensory abnormalities including head and limbs. - Visual field abnormalities. - Movement abnormalities (e.g., diffuse incoordination, tremor, chorea). • Spinal cord: - Back pain or tenderness. - Weakness and sensory abnormalities sparing the head. - Mixed upper and lower motor neuron findings. - Sensory level. - Sphincter dysfunction. • Peripheral nerve: - Mid or distal limb pain. - Weakness or sensory abnormalities following nerve distribution (see Figs. 27-2 and 27-3). - "Stocking or glove" distribution of sensory loss. - Loss of reflexes. • Muscle: - Bilateral proximal or distal weakness. - Sparing of sensation.

INVESTIGATIONS & DIAGNOSIS¶

• General Principles: - Examination may be normal in serious diseases (seizures, chronic meningitis, TIA). - Uncommon presentations of common diseases are more likely than rare etiologies. • Diagnostic Components: 1. Laboratory Assessment (Serum electrolytes, CBC, renal/hepatic/endocrine/immune studies). 2. Cerebrospinal Fluid (CSF) examination. 3. Focused Neuroimaging. 4. Electrophysiologic Studies.

Neuroimaging & Electrophysiology¶

Refer to Chapter 434 for specific details on imaging and electrophysiology.

MANAGEMENT & TREATMENT¶

• Diagnostic Approach: 1. Define the anatomy. 2. Identify the pathophysiology. 3. Take a detailed history. 4. Perform a neurologic examination. 5. Interpret clinical data to arrive at an anatomic localization. 6. Narrow the list of diagnostic possibilities. 7. Select the laboratory tests most likely to be informative. 8. Integrate findings to establish an etiological diagnosis.

Clinical Strategy¶

• Goal: Ensure technology is used judiciously, diagnosis is established efficiently, and treatment is initiated promptly.

PROGNOSIS & COMPLICATIONS¶

• Early Intervention: Essential for many neurologic disorders. - Prompt initiation of treatment once correct diagnosis is established. - Avoid over-reliance on costly imaging/labs without clinical grounding.

SPECIAL CONSIDERATIONS¶

• Systemic Predispositions: - Diabetes, hypertension, and lipids → cerebrovascular disease. - Marfan's syndrome → dissection of cranial arteries/aneurysmal SAH. - Polycystic kidney disease & fibromuscular dysplasia → aneurysmal SAH. • Drug/Toxin Specifics: - Aminoglycosides: Myasthenia gravis (weakness) or ototoxicity (dizziness). - Vincristine: Peripheral neuropathy. - Cyclosporine: Encephalopathy. - Vitamin A: Intracranial hypertension. - Pyridoxine: Peripheral neuropathy. - Alcohol: Most common neurotoxin.

KEY PEARLS & HIGH-YIELD POINTS¶

• Localization vs. Etiology: - Vertigo, diplopia, nystagmus → identify 'brainstem' or 'pons' first. • Lhermitte Syndrome: - Electric shock sensation on neck flexion → demyelination in cervical spinal cord. • Fortification Spectra: - Slowly advancing visual scotoma with luminous edges → spreading cortical depression (migraine). • Pyramidal Weakness: - Unilateral or bilateral weakness of upper limb extensors and lower limb flexors → lesion of the pyramidal tract. • Myopathy vs. Neuropathy: - Bilateral proximal weakness → myopathy. - Bilateral distal weakness → peripheral neuropathy. • Clinical Tools: - MMSE: ~85% sensitive and specific for moderate or severe dementia in educated patients. - Babinski sign: limited reliability for identifying upper motor neuron weakness; tests of tone, strength, and coordination are more useful. • Clinical Reasoning: - A patient with paraparesis and a clear spinal cord sensory level is unlikely to have vitamin B deficiency.

Reference Tables¶

TABLE 433-1 Findings Helpful for Localizations within the Nervous System Cerebrum¶

Harrison's 22e, p.3382

	SIGNS
Cerebrum	Abnormal mental status or cognitive impairment
	Seizures
	Unilateral weaknessa and sensory abnormalities including head and limbs
	Visual field abnormalities
	Movement abnormalities (e.g., diffuse incoordination, tremor, chorea)
Spinal cord	Back pain or tenderness
	Weaknessa and sensory abnormalities sparing the head
	Mixed upper and lower motor neuron findings
	Sensory level
	Sphincter dysfunction
Peripheral nerve	Mid or distal limb pain
	Weaknessb or sensory abnormalities following nerve distribution (see Figs. 27-2 and 27-3)
	“Stocking or glove” distribution of sensory loss
	Loss of reflexes
Muscle	Bilateral proximal or distal weakness
	Sparing of sensation