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SEARCH RESULTS FOR: TINNITUS

Tinnitus

Vestibular Neuritis

Vestibular Neuritis: Pathogenesis and Clinical Findings
Authors: Ryan Chan Jonathan Wong Reviewers: Mehul Gupta Davis Maclean Saud Sunba Yan Yu* Euna Hwang* * MD at time of publication
   Recent viral illness or upper respiratory tract infection
Virus spreads along upper respiratory mucosa and into the inner ear structures
Vestibular Neuritis
Presumed idiopathic viral-induced inflammation of the vestibular nerve; typically unilateral
Reactivation of Herpes Simplex Virus-1 in vestibular (Scarpa’s) ganglion
 Inflammatory cell infiltration leads to degeneration and atrophy of the vestibular nerve
    Superior Vestibular Neuritis
(40-48%) Inflammatory cells traverse through only one long bony canal, easier for inflammatory cell infiltration
Loss of afferent innervation from the superior and horizontal semicircular canal (SCC), utricle, and parts of the saccule
Combined Superior Vestibular Neuritis and Inferior Vestibular Neuritis (34-56%)
Inferior Vestibular Neuritis (1.3-18%) Inflammatory cells must pass through two separate bony canals, making inflammatory cell infiltration more difficult
Loss of afferent innervation from the posterior semicircular canal (SCC) and saccule
              Utricular degeneration
Displacement of otoliths/ otoconia (commonly into the posterior SCC)
BPPV
(can occur several months after onset of neuritis)
Loss of horizontal SCC afferent neuron signaling to the brain
Unilateral Loss or ↓ of normal nystagmus response to Caloric Testing (insertion of cold and warm water/air into the ear canal while supine)
Loss of utricular afferent neuron signaling to the brain
↓ or absent Ocular Vestibular- Evoked Myogenic Potentials (VEMPs)
and Normal Cervical VEMPs
↓ unilateral vestibular input to the brain leads to acute phase symptoms (over time, brain can compensate which allows for some symptom improvement)
Loss of posterior SCC and saccular afferent neuron signaling to the brain
↓ or absent
Cervical
VEMPs, but Ocular VEMPs are normal
     ↓ or absent input to the ipsilateral vestibular nuclei elicits a vestibular nucleus response similar to contralateral SCC excitation
Acute-Phase Spontaneous Nystagmus Fast phase beats away from the affected side (3- 10 days)
And
Loss of ocular fixation on Head Impulse Test
↓ or absent saccular input to the lateral vestibular nuclei (e.g., lateral vestibulospinal tract) results in the loss of lower limb postural adjustability
Postural Instability
(e.g., abnormal Romberg/sharpened Romberg, Fukuda step test)
Bilateral mismatch of vestibular
information to the brain
Peripheral Vertigo (lasts several hours to days; rapid onset, severe, constant)
Nausea and Vomiting
Only the vestibular
part of the vestibulo- cochlear nerve is affected, not the cochlear nerve
No Hearing
Loss or Tinnitus
            Legend:
 Pathophysiology
Mechanism
 Sign/Symptom/Lab Finding
 Complications
Published October 19, 2021 on www.thecalgaryguide.com

BPPV

Benign Paroxysmal Positional Vertigo (BPPV): Pathogenesis and Clinical Findings
Authors: Ryan Chan, Jonathan Wong, Mehul Gupta, Yan Yu* Reviewers: Davis Maclean, Saud Sunba, Euna Hwang* * MD at time of publication
Up-beating, torsional geotropic (towards the
ground) fast-phase nystagmus (towards affected side)
Down-beating +/-torsional fast-phase nystagmus (towards opposite side)
    Idiopathic Older Age
Head trauma
Recent Ear Surgery
Underlying Vestibular Disorders/Infections: Meniere’s Disease, Vestibular Neuritis, Labyrinthitis
Risk Factors of Labyrinth
Ischemia: Hypertension, Hyperlipidemia, Migraines
      Dislodged otoliths/otoconia from the macula of the utricle
Posterior Canal BPPV (~95-99%)
Superior Canal BPPV (~1%)
Horizontal Canal BPPV (~5-20%)
Ocular muscles are stimulated to generate
a downward, torsional slow-phase movement
Ocular muscles are stimulated to generate
an upward, torsional slow-phase movement
      Cupulolithiasis Theory: Otolith adheres to cupula of the semicircular canal (SCC)
Otolith displaces the cupula during head position changes resulting in prolonged sense of head rotation along the semicircular canal axis
OR
Canalithiasis Theory: Free-floating otolith in the semicircular canal (SCC)
Otolith induces inertial drag of the endolymph fluid during motion, displacing the cupula, resulting in prolonged sense of head rotation
Dix-Hallpike Maneuver: Sitting with head rotated laterally (45°), moving quickly to supine with head extended 30° off table. Observe for any nystagmus. Direction of nystagmus indicates which of the three semicircular canals is affected.
        Ocular muscles are stimulated to generate a horizontal slow-phase movement away from affected side
 Horizontal Nystagmus: Fast phase beats toward the affected side Supine Head Roll Test: lying supine, roll head laterally to each
side to move otoliths along horizontal SCC axis
     BPPV: Episodic, positional bouts of vertigo and nystagmus not due to an underlying neurological or insidious reason
If the otolith is free-floating in the SCC, movement of the affected ear towards the table generates a net stimulatory endolymph flow in the affected horizontal SCC
The stimulatory signal is carried to brainstem nuclei, generating a reflexive slow movement
of the eyes away from the affected ear, and quick horizontal movements back towards the affected ear
Geotrophic Horizontal Nystagmus: fast-phase nystagmus beats horizontally towards the table
If the otolith is adherent to the SCC cupula,
movement of the affected ear towards the table generates a net inhibitory deflection of the horizontal SCC cupula
The inhibitory signal is carried to brainstem nuclei, generating a reflexive slow movement of the eyes towards the affected ear, and quick horizontal movements away from the affected ear
Apogeotropic Horizontal Nystagmus: fast-phase nystagmus beats horizontally towards the ceiling
      Otoconia & otoliths only affect the
semicircular canal (SCC), not the cochlea
No tinnitus or hearing loss
Otoconia tend to settle quite quickly (<1 min) when body is still, resolving the mismatch of body movement & semicircular canal (SCC) excitation
Vertigo and nystagmus is transient (lasting ~1min or less)
     Legend:
 Pathophysiology
 Mechanism
 Sign/Symptom/Lab Finding
 Complications
Published January 9, 2022 on www.thecalgaryguide.com

Migraines and auras pathogenesis and clinical findings

Migraines and Auras: Pathogenesis and clinical findings Genetic mutations at certain loci (e.g., Familial hemiplegic
 migraine mutation in gene encoding P/Q-type Ca2+ channels)
    Personal triggers (e.g., lack of food, emotional stress)
“Cortical Spreading Depolarization” followed by “Cortical Spreading Depression” across one cortical hemisphere
Cortical spreading depression
creates “auras” via unknown mechanism(s)
Expanding scotoma (area of visual blurriness)
Spreading paraesthesias (numbness that travels across body)
Dysphasic language (trouble finding words)
Brainstem symptoms (e.g., vertigo, tinnitus)
Motor symptoms (e.g., hemiplegia)
 Triggering of a depolarization wave in a unilateral region of the cortex with associated ↑ blood flow to that region
Neurons and glia release K+ into extracellular space that spreads depolarization wave to nearby cortical areas
Ion gradient imbalances cause Prolonged vasoconstriction neurons in original cortical area to and ↓ blood flow
swell and become inhibited
              Activation of the hypothalamus (responsible for maintaining homeostasis)
Prodromal symptoms (↑ thirst, hunger, yawning, ↓ cognitive function)
Author:
Yan Yu
Braxton Phillips
Reviewers:
Shahab Marzoughi
Owen Stechishin
Dustin Anderson
Scott Jarvis*
Sina Marzoughi*
* MD at time of publication
Release of hypothalamic neurotransmitters (e.g., orexins, neuropeptide Y) at the trigeminalcervical complex (TCC) of the brainstem and cervical spinal cord
Depolarizing wave passes over pseudounipolar neurons (neurons with two axons) of the trigeminal ganglion which synapse in brainstem & dura matter
       These neurotransmitters reduce the activation threshold of spinal trigeminal nucleus neurons in the TCC
Neuropeptides (e.g., calcitonin gene-related peptide, pituitary adenylate cyclase-activating polypeptide)
are released at the TTC, triggering local inflammation (termed neurogenic inflammation)
Ongoing neurogenic inflammation activates secondary nociceptive neurons in the TTC
Central sensitization (↓ response threshold of secondary nociceptive neurons in the TTC)
Brain perceives referred pain from the face as the TTC also receives convergent nociceptive input from the face
Facial allodynia (pain with normally non-painful stimuli)
Serotonin & histamine are released on dural blood vessels triggering neurogenic inflammation in the dura matter
Ongoing neurogenic inflammation activates primary nociceptive neurons in the dura matter
Peripheral sensitization (↓ response threshold of primary nociceptive neurons around the dural blood vessels_
Unknown mechanisms no longer believed to be related to dural blood vessel dilation
Unilateral throbbing headache
          Legend:
 Pathophysiology
 Mechanism
 Sign/Symptom/Lab Finding
 Complications
 Published Nov 22, 2012, updated Jul 1, 2024 on www.thecalgaryguide.com

Polycythemia Vera Complications

Polycythemia Vera (PV): Complications
High numbers of cells & platelets ↑ blood viscosity
Polycythemia Vera
Hematological disorder in which JAK2 mutations in hematopoietic cells result in increased RBC production. See corresponding Calgary Guide slide “Polycythemia Vera: Pathogenesis”
    ↑ Blood cell volume
       Presence of increased numbers of platelets creates a hypercoagulable and prothrombotic state
↑ Risk of venous & arterial thrombosis
↑ Systemic vascular resistance Impaired/“sluggish” blood flow
↓ Perfusion to small vessels and ↓ oxygen delivery to throughout body
Arterial clots in arms
and legs or in vessels leading to brain prevent oxygen delivery to cells
Systemic hypertension
↑ Turnover of hematopoietic cells (RBCs, WBCs, platelets)
   Fatigue
     Transient visual disturbances
Neurological symptoms (e.g. headache, dizziness, tinnitus, concentration problems)
Breakdown of nucleic acids during cell turnover ↑ uric acid levels in blood
Lysing cells release lactate dehydrogenase (LDH) into bloodstream
↑ Spleen activity to filter and dispose of old blood cells
Splenomegaly
Authors: Caitlin Bittman Noriyah Al Awadhi Yan Yu Peter Duggan* Reviewers: Maharshi Gandhi Kevin Zhan Michelle J. Chen Paul Ratti Merna Adly Crystal Liu Kareem Jamani* Man-Chiu Poon* Lynn Savoie* * MD at time of publication
Extramedullary hematopoiesis
Pancytopenia
            Clots in the
portal vein, splenic vein, & mesenteric vein are unusual & highly suggestive of PV
Clots in cardiac arteries prevent O2 delivery to cardiac tissue
Myocardial infarction
Venous blood moves more slowly and is less pressurized compared to arterial blood. Combined with hypercoagulable state, clots are likely to form in deep veins (usually of the legs)
Deep vein thrombosis
Clot breaks off and
travels through the inferior vena cava & right heart into the pulmonary arteries
Pulmonary embolism
Stimulation fibroblasts in the bone marrow
Uric acid accumulates & precipitates in blood
Hyperuricemia
↑ Serum LDH
         Limb ischemia
Ischemic stroke & transient ischemic attacks
Erythromelalgias (burning pain in the extremities and erythema due to poor perfusion and transient microvascular occlusion)
Compensatory vasodilation in the capillaries of the skin
Plethora/rusted or “ruddy” complexion, particularly noticeable on the face, palms, nailbeds, & mucous membranes
Gout
Uric acid stones
     Advanced Disease Progression
Abnormal blood cells produced in PV release various growth factors and cytokines
Production of excess collagen and other fibrous materials
Hematopoietic cells in bone marrow replaced with fibrous tissue over time
Bone marrow increasingly unable to produce healthy blood cells
Myelofibrosis (rare type of chronic blood cancer; considered late-stage progression of PV characterized by bone marrow fibrosis)
Bone marrow failure
            Chronic bone marrow hyperactivity leads to exhaustion and/or damage of hematopoietic cells
 Legend:
 Pathophysiology
Mechanism
Sign/Symptom/Lab Finding
 Complications
 Published Aug 7, 2012, updated Feb 22, 2025 on www.thecalgaryguide.com

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