The ONSD/ETD Ratio


  • Ultrasound (6- to 13-MHz linear array ultrasonic probe from Edge (Sonosite Corporation, USA)



  1. patient supine, head in middle, eyelids closed
  2. place probe horizontally above transverse axis of eyeball
  3. slowly and vertically move to the eyeball from forehead to nose, until clearest and artifact-free optimal plane echoed on the frozen images
    1. optic nerve image = low-echo strip structure located in the front and rear of the eyeball
    2. simultaneous appearance of lens and optic nerve means ultrasound probe is on the best place
  4. Measure the following:
    1. maximum external diameter of ONSD at 3mm behind the ball
    2. maximum diameter of ETD (parallel lens)
    3. measure both eyes 3x and average values as final ONSD and ETD


Accuracy comparison:

  1. US-ONSD / ETD ratio:
    1. AUC of ROC curve 0.920
    2. threshold value 0.25 (Sn90%, Sp82.3%)
  2. US-ONSD:
    1. AUC of ROC curve 0.870
    2. threshold value 5.53 mm (Sn80%, Sp79.3%)
  3. CT-ONSD / ETD ratio:
    1. AUC of ROC curve 0.896
    2. threshold value 0.25 (Sn85.7%, Sp83.3%)


Figure.  Optic nerve ultrasound examination.

Figure.  Gray-scale image of eyeball, the ONSD is a linear hypoechoic structure posterior to the eyeball. Caliper ONSD identifies the measured point 3 mm posterior to the eyeball.

Axial CT scans showing a postoperation CT image with normal ICP.

The ONSD at 4.5 mm of the same patient. The CT-ONSD/ETD ratio is 0.19


My question – In patients at risk for delayed HCP, can this ratio predict need for VPS?


Du, J., Deng, Y., Li, H., Qiao, S., Yu, M., Xu, Q. and Wang, C. (2019). Ratio of Optic Nerve Sheath Diameter to Eyeball Transverse Diameter by Ultrasound Can Predict Intracranial Hypertension in Traumatic Brain Injury Patients: A Prospective Study. Neurocritical Care.

Enhanced Recover After Surgery (ERAS) for Neuro-oncologic Surgeries

Enhanced Recovery After Surgery (ERAS) was originally conceptualized to decrease morbidity after colorectal surgery and has since been expanded to encompass other abdominopelvic surgeries.  A review article from Journal of Clinical Neuroscience (2015) applied the ERAS concept to elective craniotomies for tumor resections to facilitate hospital discharge for cancer patients, expedite subsequent chemoradiothrapy and improve patient outcome.

The guidelines proposed include:

  1. Pre-operative
    1. Patients should routinely be counselled on what to expect from surgery. (Low, Strong)
    2. Patients should abstain from alcohol and smoking 1 month prior to surgery (Mod, Strong)
    3. Patients should be given enteral nutrition preoperatively. (Mod, Strong)
    4. Patients may benefit from immunonutrition perioperatively. (Mod, Weak)
    5. Patient should be encouraged to load with carbohydrates perioperatively.*  (Low, Strong)

*Perioperative oral CHO loading up to 2 hours prior to surgery has been shown to attenuate insulin resistance and improve subjective feelings of hunger, thirst, and post-operative fatigue compared with fasting.  As CHO beverages are a clear liquid, perioperative CHO loading should be encouraged.

  1. Intra-operative 
    1. Surgeon should minimize scalp shaving. (Mod, Weak)
    2. Cefazolin should be given within 1 hour prior to skin incision.  For patients with MRSA, vancomycin should be initiated 1 hour prior to skin incision. (High, Strong)
    3. Surgeon should utilize scalp in filtration and scalp blocks for craniotomies. (Mod, Strong)
    4. There is no evidence that short-acting anesthetics are superior to longer acting anesthetics, nor TIVA to pure inhalational anesthetics.
    5.  Minimally invasive surgery may improve patient recovery and satisfaction. (Very low, Weak)
  2. Post-operative
    1. Gabapentin / pregabalin / tramadol have side effect profiles that are unfavorable for craniotomy. (Low, Weak)
    2. Low evidence for efficacy of intravenous acetaminophen, but side effect profile is favorable.  (Mod, Strong)
    3. There may be a role for limited dosing of COX-2 inhibitors and flupirtine pending further research.  (Low, Weak)
    4. Routine serotonin receptor antagonists and dexamethasone is recommended for PONV.  (High, Strong)
    5. Aprepitant should be reserved for patients at high risk of PONV due to higher cost and limited effectiveness.  TEAS (transcutaneous electrical acupoint stimulation) requires further study.  (Low, Weak)
    6. Scopolamine and promethazine side effect profiles make them undesirable as first-line nausea meds.  (Low, Weak)
    7. Avoid hypothermia.  (High, Strong)
    8. Remove Foley on posteroperative day 1 or as early as feasible.  (Mod, Strong)
    9. Post-operative TPN not needed except for patients in prolonged comatose state.  (Mod, Strong)
    10. Encourage early mobilization.  (High, Strong)
  3. Others:
    1. Patients should use graduated compression stockings and intermittent pneumatic compression to prevent VTE.  Routine use of anticoagulants is not recommended. (High, Strong)
    2. Audit measure routinely.  (Mod, Strong)




Sample Neurosurgery-ERAS Guideline given to patients from Penn medicine: ERAS Neurosurgery


Hagan, K., Bhavsar, S., Raza, S., Arnold, B., Arunkumar, R., Dang, A., Gottumukkala, V., Popat, K., Pratt, G., Rahlfs, T. and Cata, J. (2016). Enhanced recovery after surgery for oncological craniotomies. Journal of Clinical Neuroscience, 24, pp.10-16.


Collateral Circulation Grading System

collateral circulation grading system from the American Society of Interventional and Therapeutic Neuroradiology/American Society of Interventional Radiology (ASITN/SIR)

Grade 0: No collaterals visible to the ischemic site

Grade 1: Slow collaterals to the periphery of the ischemic site with persistence of some of the defect

Grade 2: Rapid collaterals to the periphery of ischemic site with persistence of some of the defect and to only a portion of the ischemic territory

Grade, 3: Collaterals with slow but complete angiographic blood flow of the ischemic bed by the late venous phase

Grade 4: Complete and rapid collateral blood flow to the vascular bed in the entire ischemic territory by retrograde perfusion

Grade of 0-1 indicates poor collateral circulation

Grade 2 indicates moderate collateral circulation

Grades of 3-4 indicate good collateral circulation


Chen, W., Song, X., Tian, D., Sun, H., Zhang, L., Hui, X., Ip, B. and Wang, X. (2019). Clinical efficacy of collateral circulation in the evaluation of endovascular treatment for acute internal carotid artery occlusion. Heliyon, 5(4), p.e01476.

R.T. Higashida, A.J. Furlan, H. Roberts, T. Tomsick, B. Connors, J. Barr, W. Dillon, S. Warach, J. Broderick, B. Tilley, D. Sacks, I. Technology Assessment Committee of the American Society of, N. Therapeutic, R. Technology Assessment Committee of the Society of Interventional, Trial design and reporting standards for intra-arterial cerebral thrombolysis for acute ischemic stroke, Stroke 34 (8) (2003) e109ee137.

Arteriovenous Malformation Scores

Table.  Predictive grading systems for procedural risk in the endovascular treatment of brain AVMs.Capture


Buffalo score best predicts procedural risks, although predictive value is modest (AUC ~0.7).



Pulli, B., Stapleton, C., Walcott, B., Koch, M., Raymond, S., & Leslie-Mazwi, T. et al. (2019). Comparison of predictive grading systems for procedural risk in endovascular treatment of brain arteriovenous malformations: analysis of 104 consecutive patients. Journal Of Neurosurgery, 1-9. doi: 10.3171/2019.4.jns19266


Indications for Screening Dopplers on Hospital Admission

  1. known hypercoagulable disorder
  2. admitted from another institution
  3. presents with significant leg immobility
  4. presents with signs and symptoms of VTE
  5. significant critical illness
  6. significant neurotraums (TBI, SCI / TLS spine fractures)
  7. comatose
  8. known malignancy (e.g. GBM, meningioma)
  9. CKD on hemodialysis
  10. received platelet transfusion or antithrombotic reversal
  11. recent major orthopedic surgery

Order screening dopplers as “urgent” and not routine.



North Shore University Hospital VTE Prophylaxis Guidelines (Neurocritical Care)

Contrast-Induced Transient Cortical Blindness


  • Can occur with ionic or nonionic contrast media
  • MECHANISM: transient vasculopathy with disruption of BBB – a form of PRES
    • Onset within mins to hours after procedure
    • Begins with BOV –> complete blindness rapidly, associated with HA
    • Other symptoms: n/v, confusion, aphasia, memory impairment, weakness, ataxia
    • CT head: enhancement from contrast during cardiac cath, affecting cortex (parieto-occipital lobes, deep gray structures, BS, cerebellum)
    • Symmetric white matter edema in posterior cerebral hemispheres
  • Neuro impairment and neuroimaging gradually resolve over days



UpToDate. (2019). Retrieved from

Stroke After Cardiac Cath


  • Catheter or wire manipulation dislodges debris (thrombus, calcified material, cholesterol particles) from plaques within aortic arch, prox carotid / vertebral arteries
  • Fresh thrombus may form at catheter and guidewire tips
  • Less common: air embolism, thromboembolism from LV clot, periprocedural hypotension, arterial dissection, fractured guidewire
  • Hemorrhagic stroke fromthrombolytics, anticoagulants and antiplatelets used periprocedurally


  • Cardiac cath (ALL) stroke within 36h occurs: 0.1-0.6%
  • PCI: 07-0.4%
  • Hemorrhagic stroke (mostly ICH): 8-45% of cardiac cath strokes
  • SAH after cardiac cath uncommon
  • Asymptomatic radiographic infarcts after diagnostic cardiac cath: 8%
    • clinically symptomatic events (stroke+TIA): 0.6%
  • TCD: higher prevalence (up to 100%) of microemboli during cardiac cath
    • Majority occur during contrast injection (mostly air bubbles)
    • Smallernumber with movement of catheter/guidewire (mostly particles – atheromatous debris)


  • Clinical: >75-80y, HTN, DM, h/o stroke, renal failure, CHF, severity of CAD
  • Procedural: emergent, longer procedure, greater contrast, retrograde cath of LV in AS, interventions at bypass grafts, use of IABP, (+) coronary artery thrombus
  • Risks for ICH: (+) anticoagulation or thrombolytic therapy + any one of the ffg:  age >=75, femal, SBP >=160, black race, low body weight


  • Mostly during procedure or within 24h after procedure
  • Maximal deficit at onset or fluctuating course = ischemic stroke
  • Gradual worsening over minutes to hours and signs of increased ICP= hemorrhage


  • Ischemic stroke / ICH: Visual disturbance, aphasia, dysarthria, hemiparesis, AMS
  • SAH: HA, global neuro deficits, altered LOC
  • Diffuse embolization: nonfocal presentation, reduced alertness, encephalopathy



  • Activate stroke team, time of onset, last know normal (last time alert enough to be assessed, in sedated patient)
  • ABCs
  • Serum glucose
  • Platelets, coagulation studies (if suspected)
    • CT, CTA, CTP
    • Some experts advocate immediate angio + IA thrombolysis



  • TIA
  • Seizure
  • Migraine
  • Encephalopathy
  • Toxic-metabolic encephalopathy
    • Sedation from procedure
    • Co-morbid medical or neuro conditions
    • Can occur with ionic or nonionic contrast media
    • MECHANISM: transient vasculopathy with disruption of BBB – a form of PRES
      • Onset within mins to hours after procedure
      • Begins with BOV à complete blindness rapidly, associated with HA
      • Other symptoms: n/v, confusion, aphasia, memory impairment, weakness, ataxia
      • CT head: enhancement from contrast during cardiac cath, affecting cortex (parieto-occipital lobes, deep gray structures, BS, cerebellum)
      • Symmetric white matter edema in posterior cerebral hemispheres
    • Neuro impairment and neuroimaging gradually resolve over days


TREATMENT (Ischemic Stroke)

  • tPA for eligible patients (within 4.5h stroke onset)
    • safe and efficacious
    • evidence of benefit, but risk of bleeding high (recent use of antithrombotic therapy + procedural risks of bleeding)
    • studies show improved NIHSS, no difference inmortality or bleeding events
    • document normal PTT prior to IV tPA if heparin given within 48h
    • protamine can be used to reverse heparin
    • GP2B3A – unknown if may increase risk of bleed with tPA, but preliminary data suggests safety
    • Single or DAPT not contraindication
  • mechanical thrombectomy (within 6h)
  • IA alteplase in 4.5-6h time window if not eligible for tPA but eligible for thrombectomy

TREATMENT (Hemorrhagic Stroke)

  • Reversal of anticoagulation, stop all anticoagulants and antiplatelets
  • BP control
    • labetalol, nicardipine, esmolol, enalapril, hydralazine, nitroprusside, NTG
    • <=185/110 if tPA given
    • <=220/120 if no tPA given
  • Treatment of ICP
    • HOB 30 degrees, analgesia (morphine, alfentanil), sedation (propofol, etomidate, midazolam)
    • Mannitol, EVD, NM blockade, hyperventilation
    • ICP monitoring, goal CPP>70mm Hg
  • Surgery
    • Cerebellar bleed >3cm with BS compression / hydrocephalus – surgical evacuation
    • Supratentorial bleed: consider crani only for lobar clots within 1cm of surface


  • Stroke after cardiac cath: high in-hospital and 30d mortality rate
  • 30d mortality rate after PCI
    • 19% (ischemic stroke)
    • 50% (hemorrhagic)
    • 2% (if no stroke)



UpToDate. (2019). Retrieved from

How to Measure Transcalvarial Herniation

The volume of brain tissue herniated through the craniectomy (TCH) can be measured according to the model proposed by Liao et al. Based on trigonometry and the mathematical concepts of radius and diameter of a sphere (skull), a formula was created that uses simple measurements of the values and differences between height (h) of the apparently normal contralateral side of the brain and that of the side of herniation. Fig. 1 illustrates the method used to calculate the volume of TCH in millimeters.


Neto, A., et al. Clinical Neurology and Neurosurgery. Transcalvarial brain herniation volume as a predictor of posttraumatic hydrocephalus after decompressive craniectomy.

C.C. Liao, Y.H. Tsai, Y.L. Chen, K.C. Huang, I.J. Chiang, J.M. Wong, F. Xiao, Transcalvarial brain herniation volume after decompressive craniectomy is the difference between two spherical caps, Med. Hypotheses 84 (3) (2015)(2015)