What is the best management approach for a patient experiencing nighttime dizzy spells, potentially related to a myeloproliferative neoplasm?

Management of Nighttime Dizzy Spells in Myeloproliferative Neoplasm Patients

Nighttime dizzy spells in a patient with myeloproliferative neoplasm require immediate evaluation for hyperviscosity syndrome, thrombotic events, and anemia, with management directed at the underlying hematologic abnormality through cytoreduction and optimization of blood counts.

Initial Assessment Priority

The dizzy spells must be evaluated in the context of the MPN's hematologic parameters, as these symptoms likely reflect disease-related complications rather than primary vestibular pathology 1.

Critical Laboratory Evaluation

• Hematocrit levels: Target maintenance below 45% is essential, as elevated hematocrit significantly increases thrombotic risk (HR 3.91 for cardiovascular events when hematocrit is 45-50% vs <45%) 1
• Platelet count: Extreme thrombocytosis (>1,500 × 10⁹/L) paradoxically increases bleeding risk and can cause cerebrovascular symptoms 1, 2
• Hemoglobin: Values <10 g/dL indicate severe anemia requiring treatment 1
• White blood cell count: Target <10 × 10⁹/L to reduce hyperviscosity 3, 2

Mechanism-Based Differential

Hyperviscosity-related dizziness occurs when:

• Hematocrit exceeds 45% in polycythemia vera 1
• Platelet counts exceed 1,500 × 10⁹/L 1, 2
• Leukocytosis is uncontrolled 3

Anemia-related dizziness manifests when hemoglobin drops below 10 g/dL, particularly common in primary myelofibrosis 1

Thrombotic events (including transient ischemic attacks) present as episodic dizziness and represent medical emergencies 1

Treatment Algorithm

For Polycythemia Vera Patients

Step 1: Immediate phlebotomy if hematocrit ≥45%

• Remove 300-450 mL weekly or twice weekly until target achieved 1
• Continue low-dose aspirin 81-100 mg daily unless contraindicated 1, 3

Step 2: Initiate cytoreductive therapy if:

• Age >60 years 1, 3
• Prior thrombotic event 1, 3
• Poor phlebotomy tolerance 1
• Symptomatic splenomegaly 1
• Platelet count >1,500 × 10⁹/L 1, 2

First-line cytoreduction: Hydroxyurea at 2-2.5 g/day (higher dose for patients >80 kg) 2, 4

For Essential Thrombocythemia Patients

Cytoreductive therapy indicated when:

• High-risk features present (age >60, prior thrombosis) 3, 2
• Platelet count >1,500 × 10⁹/L 1, 2
• Progressive symptoms 1

Target platelet count: <400 × 10⁹/L 3, 2

For Primary Myelofibrosis Patients

Anemia management when hemoglobin <10 g/dL:

• Corticosteroids (prednisone 0.5-1.0 mg/kg/day) 1
• Androgens (testosterone enanthate 400-600 mg weekly) 1
• Danazol 600 mg/day 1
• Lenalidomide if del(5q) present 1

Constitutional symptoms (including dizziness):

• Often respond to splenomegaly treatment 1
• Hydroxyurea for symptomatic splenomegaly 1

Monitoring and Adjustment

Reassess every 3-6 months for:

• New thrombotic or bleeding events 3
• Disease-related symptom progression 3
• Blood count targets: hematocrit <45%, platelets <400 × 10⁹/L, WBC <10 × 10⁹/L 3, 2

Hydroxyurea resistance/intolerance defined by:

• Platelet count >600 × 10⁹/L after 3 months at adequate dosing 2, 4
• Hemoglobin <10 g/dL at current dose 4
• Mucocutaneous manifestations or leg ulcers 2, 4

Second-line options:

• Anagrelide for essential thrombocythemia 2
• Interferon-alpha or ruxolitinib for polycythemia vera 2, 4

Critical Pitfalls to Avoid

Do not attribute dizziness to benign causes without first optimizing hematologic parameters, as the CYTO-PV trial demonstrated a nearly 4-fold increase in cardiovascular events with suboptimal hematocrit control 1

Avoid hydroxyurea dose escalation beyond 2.5 g/day in patients >80 kg; instead, switch to second-line therapy if targets not achieved 2, 4

Aggressively manage cardiovascular risk factors (hypertension, diabetes, hyperlipidemia) as these compound thrombotic risk 1, 3

Monitor for extreme thrombocytosis as platelets >1,500 × 10⁹/L create acquired von Willebrand disease with bleeding risk 3, 2