How to manage a patient with thrombocytosis (elevated platelet count) and vertigo?

Management of Thrombocytosis with Vertigo

The primary task is to determine whether the thrombocytosis is primary (myeloproliferative neoplasm) or secondary (reactive), as this fundamentally changes management—secondary thrombocytosis requires no platelet-directed therapy and vertigo should be evaluated as an independent symptom, while primary thrombocytosis may require cytoreductive therapy and the vertigo could represent a thrombotic complication. 1

Initial Diagnostic Approach

Obtain a complete blood count with peripheral blood smear to distinguish primary from secondary thrombocytosis. 1 This distinction is critical because:

• Secondary thrombocytosis does not require antiplatelet therapy or platelet-directed treatment, as platelet function remains normal and thromboembolic complications are extremely rare. 1
• Treatment should focus exclusively on the underlying condition causing reactive thrombocytosis. 1

Evaluation of Vertigo in the Context of Thrombocytosis

If Primary Thrombocytosis (Myeloproliferative Neoplasm):

Consider vertebrobasilar thrombosis as a potential life-threatening cause of vertigo, particularly if neurological symptoms are present. 2 Key features to assess:

• Perform careful neurological examination looking for additional brainstem signs beyond isolated vertigo (diplopia, dysarthria, ataxia, crossed sensory findings). 2
• Vertigo from basilar artery thrombosis can initially present with isolated vestibular symptoms that mimic benign peripheral disorders. 2, 3
• If any atypical features exist (negative or atypical Dix-Hallpike testing, associated neurological symptoms, lack of response to repositioning maneuvers), obtain urgent neuroimaging. 4

If Secondary Thrombocytosis:

Evaluate vertigo as an independent symptom unrelated to platelet count. 1 The diagnostic approach follows standard vertigo evaluation:

• For brief episodic vertigo triggered by head movements with typical nystagmus on Dix-Hallpike testing, diagnose benign paroxysmal positional vertigo (BPPV) clinically without imaging. 4
• Imaging is unnecessary for typical BPPV but should be obtained if atypical features are present. 4

Management of Primary Thrombocytosis

Cytoreductive Therapy:

Anagrelide is FDA-approved for treating thrombocythemia secondary to myeloproliferative neoplasms to reduce elevated platelet count and thrombosis risk. 5

• Starting dose: 0.5 mg orally once daily or 0.5 mg twice daily. 5
• Adjust dose weekly until platelet count reaches 150,000-400,000/μL or reduces by at least 50% from baseline. 5
• Maximum dose: 12 mg daily. 5
• Common side effects include cardiovascular effects (palpitations, chest pain), which patients should report immediately. 5

Antiplatelet Therapy Considerations:

For patients with JAK2-mutated essential thrombocythemia or cardiovascular risk factors, aspirin is recommended. 4

• In extreme thrombocytosis (platelet count >1 million/μL), rule out acquired von Willebrand syndrome before starting aspirin, as this increases bleeding risk. 4
• Aspirin should be avoided if acquired von Willebrand syndrome or bleeding events are present. 4

Anticoagulation for Thrombotic Events:

If vertebrobasilar or other thrombosis is confirmed, initiate immediate anticoagulation with heparin to prevent progression. 2

• Therapeutic low-molecular-weight heparin (LMWH) is prescribed for documented venous thromboembolism. 4
• Age-dependent LMWH dosing for enoxaparin: <2 months = 1.5 mg/kg/dose every 12 hours; ≥2 months = 1.0 mg/kg/dose every 12 hours. 4

Management of Secondary Thrombocytosis

No antiplatelet therapy or platelet-directed treatment is necessary, as it provides no benefit and increases bleeding risk. 1

• Focus treatment exclusively on the underlying condition causing reactive thrombocytosis. 1
• Thromboembolic complications are extremely rare in secondary thrombocytosis, with no reports in over 1,000 children studied. 1

Critical Pitfalls to Avoid

Do not dismiss vertigo as benign peripheral vestibular disease without careful neurological examination, especially in primary thrombocytosis. 2 Basilar artery thrombosis can present with isolated vestibular symptoms initially, and delayed diagnosis is associated with high mortality. 2

Do not prescribe antiplatelet therapy for secondary thrombocytosis—this is contraindicated and increases bleeding risk without benefit. 1

Do not start aspirin in extreme thrombocytosis without first excluding acquired von Willebrand syndrome, as paradoxical bleeding can occur. 4

Monitor for cardiovascular side effects when using anagrelide, including palpitations, chest pain, and irregular heartbeat, which require immediate evaluation. 5