Numbness and Weakness

Paresthesia and Weakness

Objectives - General

Generate a differential diagnosis for paresthesias.
Describe the normal physiology of sensation.
Describe the pathophysiology of common causes of paresthesias.
Generate a differential diagnosis for weakness.
Describe the normal physiology of strength.
Describe the pathophysiology of common causes of weakness.
Implement an organized approach to the evaluation and initial management of patients presenting with numbness and/or weakness.
- Use patient information such as HPI, past medical history, family history, social history, and ROS to narrow a differential diagnosis.
- Select appropriate physical exams that should be performed, utilizing their positive and negative findings to further refine the differential diagnosis.
- Choose appropriate diagnostic tests when indicated and utilize these results to narrow the differential diagnosis or confirm a working diagnosis.

Objectives - Specific

Define paresthesia.
Describe the sensory pathway from the periphery to the CNS.
Define weakness.
Describe the motor pathway from the brain to the muscles.
Define stroke and transient ischemic attack (TIA).
List risk factors for stroke.
Distinguish between ischemic and hemorrhagic strokes.
State the most common causes of ischemic stroke and give examples.
Identify the artery most often involved in ischemic stroke.
Recognize symptoms of a stroke involving the MCA (Middle Cerebral Artery).
Describe basic principles of stroke treatment.
Define radiculopathy and describe disc herniation.
State the most common cause of radiculopathy and describe sensory and motor changes associated with it.
Explain general principles of herniated disc treatment.
Define peripheral neuropathy and describe mononeuropathies versus polyneuropathy, listing common causes.
Describe mononeuritis multiplex and diabetic neuropathy, including their pathophysiology and complications.
Describe autonomic neuropathy, compression neuropathy, and specifically carpal tunnel syndrome.
Outline myasthenia gravis, its cause, pathophysiology, symptoms, and management principles.
Describe herpes zoster (shingles), its cause and complications.
Discuss multiple sclerosis (MS) including its pathophysiology, symptoms, and clinical management.
Describe amyotrophic lateral sclerosis (ALS) and Guillain-Barré syndrome, including their pathophysiological mechanisms and clinical presentations.

Paresthesia

Definition: An abnormal sensation of the skin that may feel like tingling, prickling, burning, or numbness. Commonly referred to as "numbness and tingling."

Components Required for Normal Sensation

Dorsal column-medial lemniscal pathway:
- First-order neurons (afferent): Proprioceptors or mechanoreceptors located in the spinal cord.
- Second-order neurons: Dorsal column nuclei process information at the level of the medulla oblongata. The process consists of decussation of the medial lemniscus.
- Third-order neurons: Located in the thalamus, relaying information to the primary somatosensory cortex.
Spinothalamic tract:
- Includes sensory pathway for nociceptors and thermoreceptors.

What Could Go Wrong in Sensory Pathways?

Problems at any of the levels (e.g., first-order, second-order, third-order neurons, thalamus, and cortex) could lead to abnormal sensations such as paresthesia.

Weakness

Definition: A lack of strength that is different from fatigue.

Components Required for Normal Strength

Motor pathway components:
- Upper motor neurons (UMN) in the cerebrum descend through the internal capsule and midbrain.
- Lower motor neurons (LMN) in the spinal cord activate skeletal muscle at the neuromuscular junction after traversing corticospinal tracts.
- Involves decussation in pyramids of the medulla oblongata and peripheral nerves.

What Could Go Wrong with Muscle Strength?

Abnormalities could originate from UMN and LMN lesions, affecting the upper cortex down to the peripheral nerves.

Case A

Patient: 72-year-old man with acute right-sided weakness and loss of sensation after breakfast.
- Key observations: Inability to move right arm/leg and difficulty speaking, suggestive of a possible stroke.

Stroke Definitions

Stroke: Sudden onset of a focal neurologic deficit that persists for at least 24 hours.
Transient Ischemic Attack (TIA): Focal neurologic deficit that lasts less than 24 hours (typically resolves within 1-2 hours).
Strokes result from abnormal cerebral circulation, with the brain receiving about 15% of resting cardiac output and consuming 20% of the body's oxygen.
Main risk factors include:
- Hypertension
- Hypercholesterolemia
- Diabetes
- Smoking

Types of Stroke

Ischemic Stroke (~87%): Results from impairment of blood supply and oxygenation to CNS tissue, usually due to embolism or thrombosis.
Hemorrhagic Stroke: Results from ruptured CNS vessels, often associated with hypertension, aneurysms, or vascular malformations.

Ischemic Strokes

Focal symptoms correlate with areas supplied by affected blood vessels, typically involving the Middle Cerebral Artery (MCA). It carries over 80% of blood flow to the cerebral hemisphere.
Most common causes include:
- Cardiac mural thrombi (atrial fibrillation, myocardial infarct)
- Thrombus due to atherosclerotic plaques (most common sites: carotid bifurcation, middle cerebral artery origin, basilar artery ends)
- Hypercoagulable states and history of drug abuse.

Circle of Willis

Major anatomic structure connecting the internal carotid and vertebral arteries, providing collateral circulation in cerebral blood supply.

MCA Stroke Specifics

Signs include decreased motor strength and sensation on one side, increased deep tendon reflexes, and possible aphasia.
The assessment of stroke can utilize the FAST (Face, Arms, Speech, Time) method to identify signs of stroke promptly.

Stroke Management

Diagnostic imaging: CT scan to assess for ischemia or hemorrhage.
Management of ischemic strokes may include:
- Intravenous thrombolysis or mechanical thrombectomy.
For hemorrhagic strokes, control blood pressure and intracranial pressure; mechanical intervention may be needed for decompression.

Case B

Patient: 54-year-old man with back pain radiating to the right leg, numbness, and weakness.

Radiculopathy

A condition characterized by pain/numbness/tingling/weakness due to damaged nerve root, commonly caused by:
- Mechanical compression (e.g., intervertebral disk herniation, degenerative disc disease).
- Typical sites: L4–L5, L5–S1, C5-C6, or C6-C7.
- Identifying features in examinations include diminished sensation and reflexes dependent on the affected area.

Disc Herniation

A tear in the anulus fibrosus allows the nucleus pulposus to bulge out, commonly linked to aging.
Internal disc pressure can significantly increase when sitting or bending, leading to disc issues, particularly posteriorly.

Neuropathic Pain

Pain that arises from damaged nerves, characterized by possible burning sensations, hypersensitivity, and specific physiological responses including mechanosensitivity and spontaneous activity.

Peripheral Neuropathies

Damage to peripheral nerves; can occur as:
- Axonal Neuropathies: Where the axons are primarily affected, leading to gradual losses.
- Demyelinating Neuropathies: Where myelin sheaths are primarily affected.
- Mononeuropathies: Affecting single nerve, often seen due to trauma or entrapment.
- Common examples include Carpal Tunnel Syndrome, affecting the median nerve.
- Polyneuropathies: Involving multiple nerves symmetrically; for example, stemming from diabetes or B12 deficiency.

Diabetic Neuropathy

The leading cause of peripheral neuropathy affecting up to 50% of diabetes patients, often presenting as symmetrical sensorimotor polyneuropathy.
- Pathogenesis involves complex mechanisms including hyperglycemia, inflammation, and ischemic factors.

Compression Neuropathy

Occurs when nerves are subjected to persistent pressure. Carpal Tunnel Syndrome is a prominent example affecting the median nerve at the wrist due to anatomical pressure.

Myasthenia Gravis

An autoimmune neuromuscular disorder with antibodies against acetylcholine receptors.
- Symptoms include muscle fatigue and weakness, particularly with repeated use, improving with rest.
- Diagnosis involves clinical tests and antibody identification.
- Treatment includes acetylcholinesterase inhibitors and immunosuppressive therapies.

Varicella-Zoster Virus

Causes herpes zoster (shingles), presenting with painful and vesicular rash along dermatomes, often accompanied by post-herpetic neuralgia characterized by persistent pain in previously affected areas.

Multiple Sclerosis (MS)

An autoimmune demyelinating disease of the CNS, often presenting with varied neurological symptoms, particularly vision loss and motor impairment.
- Diagnosis includes CSF analysis and MRI showing lesions.
- Chronic management involves immunomodulatory therapies.

Amyotrophic Lateral Sclerosis (ALS)

A degenerative disorder impacting both upper and lower motor neurons, resulting in progressive muscle weakness and atrophy, generally with a poor prognosis.

Guillain-Barré Syndrome

An autoimmune condition where the immune system attacks peripheral nerves, usually triggered by infections or vaccinations. Treatment focuses on reducing circulating antibodies via plasmapheresis or IVIG.

Non-Neuro Causes of Weakness

Include various muscle diseases such as myositis, muscular dystrophies, and inflammatory diseases; these can be distinguished using imaging and laboratory assessments.
Flashcard #1
Term: Paresthesia
Definition: An abnormal sensation of the skin that may feel like tingling, prickling, burning, or numbness.
Flashcard #2
Term: Sensory Pathway
Definition: The pathway from the periphery to the CNS includes first-order neurons (afferent), second-order neurons in the dorsal column nuclei, and third-order neurons in the thalamus, leading to the primary somatosensory cortex.
Flashcard #3
Term: Weakness
Definition: A lack of strength that is different from fatigue.
Flashcard #4
Term: Motor Pathway
Definition: The pathway from the brain to the muscles, involving upper motor neurons (UMN) from the cerebrum and lower motor neurons (LMN) in the spinal cord.
Flashcard #5
Term: Stroke
Definition: Sudden onset of a focal neurologic deficit that persists for at least 24 hours.
Flashcard #6
Term: Transient Ischemic Attack (TIA)
Definition: Focal neurologic deficit that lasts less than 24 hours, typically resolving within 1-2 hours.
Flashcard #7
Term: Risk Factors for Stroke
Definition: Include hypertension, hypercholesterolemia, diabetes, and smoking.
Flashcard #8
Term: Ischemic Stroke
Definition: Results from impaired blood supply and oxygenation to CNS tissue, typically due to embolism or thrombosis.
Flashcard #9
Term: Hemorrhagic Stroke
Definition: Results from ruptured CNS vessels, often associated with hypertension, aneurysms, or vascular malformations.
Flashcard #10
Term: Middle Cerebral Artery (MCA)
Definition: The artery most often involved in ischemic stroke, carrying over 80% of blood flow to the cerebral hemisphere.
Flashcard #11
Term: Symptoms of MCA Stroke
Definition: Include decreased motor strength and sensation on one side, increased deep tendon reflexes, and possible aphasia.
Flashcard #12
Term: FAST Method
Definition: A method to assess stroke: Face drooping, Arm weakness, Speech difficulties, and Time to call emergency services.
Flashcard #13
Term: CT Scan in Stroke Management
Definition: Used to assess for ischemia or hemorrhage in stroke patients.
Flashcard #14
Term: Intravenous thrombolysis
Definition: A treatment for ischemic strokes that involves the administration of clot-dissolving medication.
Flashcard #15
Term: Mechanical Thrombectomy
Definition: An intervention for ischemic strokes to physically remove the clot.
Flashcard #16
Term: Radiculopathy
Definition: A condition characterized by pain, numbness, tingling, or weakness due to damaged nerve roots.
Flashcard #17
Term: Disc Herniation
Definition: A tear in the anulus fibrosus allowing the nucleus pulposus to bulge out, commonly due to aging.
Flashcard #18
Term: Neuropathic Pain
Definition: Pain arising from damaged nerves, characterized by burning sensations and hypersensitivity.
Flashcard #19
Term: Axonal Neuropathies
Definition: Neuropathies where the axons are primarily affected, leading to gradual losses.
Flashcard #20
Term: Demyelinating Neuropathies
Definition: Neuropathies where myelin sheaths are primarily affected.
Flashcard #21
Term: Mononeuropathies
Definition: Affecting single nerve, often due to trauma or entrapment, such as Carpal Tunnel Syndrome.
Flashcard #22
Term: Polyneuropathies
Definition: Involving multiple nerves symmetrically; commonly associated with diabetes or B12 deficiency.
Flashcard #23
Term: Diabetic Neuropathy
Definition: The leading cause of peripheral neuropathy, presenting as symmetrical sensorimotor polyneuropathy.
Flashcard #24
Term: Compression Neuropathy
Definition: Occurs when nerves are subjected to persistent pressure, exemplified by Carpal Tunnel Syndrome.
Flashcard #25
Term: Myasthenia Gravis
Definition: An autoimmune neuromuscular disorder with antibodies against acetylcholine receptors.
Flashcard #26
Term: Herpes Zoster (Shingles)
Definition: Caused by Varicella-Zoster Virus, presenting with a painful rash along dermatomes.
Flashcard #27
Term: Multiple Sclerosis (MS)
Definition: An autoimmune demyelinating disease of the CNS, presenting with varied neurological symptoms.
Flashcard #28
Term: Amyotrophic Lateral Sclerosis (ALS)
Definition: A degenerative disorder affecting both upper and lower motor neurons, resulting in muscle weakness.
Flashcard #29
Term: Guillain-Barré Syndrome
Definition: An autoimmune condition where the immune system attacks peripheral nerves.
Flashcard #30
Term: Non-Neuro Causes of Weakness
Definition: Include muscle diseases such as myositis and muscular dystrophies, distinguished using imaging and tests.
Flashcard #31
Term: Stroke Treatment Principles
Definition: Basic principles of stroke treatment include fast assessment, stabilization of the patient, and the use of diagnostic tools such as CT scans to determine the type of stroke.
Flashcard #32
Term: Identifying Features of Radiculopathy
Definition: Specific identifying features of radiculopathy may include symptoms based on the area affected, such as diminished reflexes and specific sensory loss associated with particular nerve roots.
Flashcard #33
Term: Mononeuritis Multiplex
Definition: A condition characterized by damage to multiple peripheral nerves, often due to systemic diseases like vasculitis or diabetes, typically presenting with sensory and motor changes in affected areas.
Flashcard #34
Term: Autonomic Neuropathy
Definition: A form of peripheral neuropathy affecting autonomic nerves, which can lead to dysfunctions in involuntary bodily functions, such as digestion, heart rate, and blood pressure.
Flashcard #35
Term: Compression Neuropathy - Carpal Tunnel Syndrome
Definition: A common compression neuropathy affecting the median nerve, leading to symptoms such as numbness and tingling in the hand, often exacerbated by repetitive wrist movements.
Flashcard #36
Term: Treatments for Herniated Disc
Definition: General treatment approaches for herniated discs may include physical therapy, pain management, corticosteroid injections, and in some cases, surgical interventions if conservative measures fail.
Flashcard #37
Term: General Management of Multiple Sclerosis (MS)
Definition: Treatment for MS involves disease-modifying therapies, symptomatic treatment, and management of acute relapses with corticosteroids.