neurosono debate- with Dr Lee

[byungin]

 TCD :

개원가에서 TCD 를 많이 사용하고 있으나, 두통에서는 Reversible cerebral vasoconstriction syndrome (RCVS) 외에는 진단가치가 낮음. 

(1) TCD의 적응증 (NSRG에서 권고하는 질환들이 있던 것으로 기억합니다. 가장 긴요한 적응증은 sickle cell anemia로 알고 있습니다. )

(2) TCD로 진단이 불가능한 뇌동맥 질환들: 예를들어 aneurysm, migraine(이용석 선생님의 옛날 논문이 하나 있는 것으로 기억하지만, 그 후로는 관련논문을 본 적이 없음),

(3) 대학병원에서의 용도 ( 노인환자가 많은 뇌경색 연구에 TCD가 널리 사용되지 못할텐데, )

 > sonothrombolysis

> IV thrombolysis 후 monitoring을 통해 reocclusion or recanalization여부 판정( headset 이용)

> Microembolic signal detection

> Breathing holding index(vasomotor reactivity)> collateral pathway를 통한 reservoir의 평가를 통한 추후 뇌경색 재발 가능성 예측

> PFO test를 통한 right to Left shunt를 평가하고 parodoxical embolism을 통한 young age cryptogenic stroke의 위험도 평가

> PFO test는 migraine의 risk도 올리는 것으로 알려져 있는 것 같습니다.?(저도 migraine환자에서 해보지는 않습니다)

> 기타 cervicogenic dizziness에서 vertebrobasilar flow 평가? (예를 들면 bow hunter syndrome등)

(4) poor window 일때 어떻게 하는지. 2분 시도해 보고 안되면 포기하는게 좋다거나, 비용을 할인한다거나...

 > 비용을 할인 하거나 하지않습니다.

 > poor temporal window인지 occlusion인지 감별포인트는 뒷쪽 PCA가 잘 잡히는지 depth를 올려 반대쪽 MCA/ACA 를 잡아 보는지 등이 도움이 될 수 있습니다. 그전에 급성기 뇌졸중 TCD에서 3분정도 하라고 했습니다만(능숙한 검사자). 대학병원에서도 장비를 움직여 가면서 급성기에 이용하는 경우는 많지 않아 보입니다.

(5) 전통적으로 검사하는 동맥 외의 혈관들, 예를 들어, PcomA, SCA, 또는 그 외의 artery 또는 vein 을 보는 술기가 있는지...

> vein이나 다른 artery에 사용해 본것은 없습니다.

Carotid

(1) 다른 risk 없고, 중년에서 IMT 증가만 2 mm 정도 있을 때 어떻게 하는지?   이 정도 IMT 증가만 있어도 risk factor 로 간주하고 antiplatelet을 처방하는지?

> 저는 일단 다른 risk를 고려합니다. 아직 Treat the IMT 정도는 안닌 것 같습니다. 다른 risk factor가 없다면

 FU하는 정도....(개인적으로는 risk factor없이 증가해있는 경우는 거의 없었던 것 같습니다.)

(2) 건강한 30대 여자에게서 ICA 와 CCA 의 혈류속도 양측이 차이가 50% 이상 날 때, 병적인지 아닌지?

> 단순 50% 차이는 이상해보입니다. 다 아시는 정도로, waveform을 분석해서 낮아 있는 쪽은 post stenotic waveform change만 아니라면, 증가된쪽의 문제는 감소된 쪽의 문제인지, 측정당시 angle correction과 physilogic variation의 가능성등을 고려해야 한다고 생각합니다.

(3) CCA 의 spectrum 모양이 건강인에서도 사람마다 다양한데, 어떤 의미인지?

> 잘 모르겠습니다.

(4) 심한 ICA 협착일 때, 대학병원급으로 보내야 하는데, 지역마다 어느 병원에서 어떤 시술에 강점이 있는지 대략적인 현황.

> 이것도 답변드리기가.... 

Clinical Policy Bulletin: Transcranial Doppler Ultrasonography   

http://www.aetna.com/cpb/medical/data/300_399/0353.html

Aetna considers transcranial Doppler ultrasonography (TDU) medically necessary when used for any of the following indications: 

1. Assessing patterns and extent of collateral circulation in persons with known regions of severe stenosis or occlusion; or
2. Assessing persons suspected of having patent foramen ovale/paradoxical embolism (symptoms include visual disturbance, weakness, hemiplegia, or slurred speech); or
3. Assessing persons with suspected brain death; or
4. Assessing stroke risk of children (2 to 16 years of age) with sickle cell anemia (although the optimal time is unknown, accepted guidelines state that re-screening should be considered approximately every 6 months); or
5. Detecting arteriovenous malformations (AVMs) and studying their supply arteries and flow patterns; or
6. Detecting microemboli in cerebral artery embolism; or
7. Detecting severe stenosis in the major basal intracranial arteries for members who have neurological signs or symptoms or carotid bruits; or
8. Diagnosing dissection of vertebral artery; or
9. Eval‎uating and following persons with vasoconstriction of any cause, especially after subarachnoid hemorrhage; or
10. Eval‎uating very low birth weight preterm infants with gestational age less than 30 weeks.

     On the other hand, the assessment indicated that available data do not support the use of TDU for: (i) diagnosing or monitoring response to anti-thrombotic therapy in ischemic cerebrovascular disease; (ii) predicting outcome in vertebrobasilar distribution stroke; (iii) predicting hemorrhagic transformation of ischemic infarction; (iv) detecting impaired cerebral hemodynamics distal to high-grade extracranial internal carotid artery stenosis or occlusion; and (v) eval‎uating adults with sickle cell anemia. 

    TCD is probably useful for detection of cerebral MES in various cardiovascular and cerebrovascular disorders and procedures (Sloan et al, 2004).
     In patients with aortic embolism, patients with plaques greater than or equal to 4 mm morefrequently had MES compared with patients with smaller plaques (p = 0.04).  Data were insufficient to reliably predict future events in patients with intra-cranial stenosis, cervical artery dissection, and aortic embolism.  The authors concluded that MES are a frequent finding in varying sources of arterial brain embolism; and MES detection is useful for risk stratification in patients with carotid stenosis.
    Cerebral emboli are particles of thrombus or atheromatous plaque, platelet aggregates, lipid or air particles in cerebral circulation, which can occlude arterioles and cause TIA or stroke.  Most frequently, they derive from exulcerated plaques of the carotid bifurcation or the aortic arch, from the atrial thrombus, prosthetic heart valves, as well as during carotid endarterectomy, arterial stent, aortocoronary by-pass.  For MES detection, bilateral monitoring of a. cerebri mediae (ACM) is performed with each probe held in place over a temporal bone.
    Woitalla and colleagues (2010) stated that Imaging of the brain structure with trans-cranial ultrasound has become an important tool for the diagnosis and differential diagnosis of Parkinson's Disease 

11. CPT Codes / HCPCS Codes / ICD-9 Codes
    CPT codes covered if selection criteria are met:
    362.30 - 362.34 Retinal vascular occlusion 
    368.10 Subjective visual disturbance, unspecified 
    368.11 Sudden visual loss 
    368.12 Transient visual loss 

13. Finally, TCD may be the only mean possible to eval‎uate intracranial vessels in cases when other radiographic means are contraindicated.

14. TCD can also be used to observe the effectiveness of thrombolytic treatment in stroke patients. If the vessel is not recannulized, other treatments can be considered.

15. Monitoring for Sources of Emboli during Procedures

16. Testing for Cerebrovascular Autoregulation
    The breath-holding test is used to assess cerebrovascular reactivity to hypercapnia as calculated by means of the breath-holding index (BHI). The index is calculated by dividing the percent increase in mean FV (MFV) during breath-holding by the breath-holding time (in seconds) that subjects held their breath after a normal inspiration: BHI = {[MFV at the end of breath-holding − resting MFV]/resting MFV} × (100/seconds of breath-holding).
    This technique can be useful in testing the candidacy of asymptomatic patients with internal carotid artery stenosis for endarterectomy surgery. Recent data37 showed increased risk of ischemic strokes in patients with severe (>70%) carotid stenosis and impaired autoregulation as tested by TCD. TCD can also assess the potential risk of cerebral ischemia in patients with carotid stenosis going for major anesthesia and surgery. TCD might also be a useful investigation in work up of a patient with vasovagal syncope38–41.

[byungin]

Limitation of TCD:
examination of cerebral blood flow velocities in certain segments of large intracranial vessels
detects indirect effects (abnormal waveform characteristics) suggesting of proximal hemodynamic or distal obstructive lesions
more valuable in specific conditions