Head computed tomography for subarachnoid hemorrhage diagnosis [Neurosurgery Wiki]

This page is read only. You can view the source, but not change it. Ask your administrator if you think this is wrong.
====== Head computed tomography for subarachnoid hemorrhage diagnosis ======

{{rss>https://pubmed.ncbi.nlm.nih.gov/rss/search/1neszevTVzpU8km79c-5wruiV7nnaM17EjKzWAdx8p36pZHMoq/?limit=15&utm_campaign=pubmed-2&fc=20240104070942}}
----

----

A good quality (e.g. no motion artifact) non-contrast high-resolution [[Head computed tomography]] will detect SAH in ≥ 95% of cases if scanned within 48 hrs of SAH. Blood appears as high density (white) within [[subarachnoid space]]s.

For subtle SAH findings, look in the [[occipital horn]]s of the [[lateral ventricle]]s and the dependent portions of the [[Sylvian fissure]]s. 
----
Acute headache may be the primary symptom of subarachnoid hemorrhage (SAH). Guidelines suggest that non-contrast computed tomography (CT) is adequate to exclude aneurysmal SAH if performed within 6 h after symptom onset. However, most studies of acute headache including CT, lumbar puncture and SAH are multicenter studies from referral hospitals with highly selected patient populations.
In acute headache, a CT scan taken within 6 h is practically 100% sensitive for detecting any SAH
((Aaseth K, Dhami SKG, Kravdal G, Zarnovicky S, Faiz KW, Vetvik KG, Kristoffersen ES. Diagnostic workup of acute headache and subarachnoid hemorrhage in a Norwegian population: An observational study. Eur J Neurol. 2024 Sep;31(9):e16385. doi: 10.1111/ene.16385. Epub 2024 Jun 22. PMID: 39092827; PMCID: PMC11295164.))
----
CT also assesses:

1. ventricular size: hydrocephalus occurs acutely in 21% of aneurysmal ruptures.

2. hematoma: [[intracerebral hemorrhage]] or large amount of subdural blood with mass effect may
need emergent evacuation

3. infarct: not sensitive in first 24 hours after infarct 

4. amount of blood in cisterns and fissures: important prognosticator for vasospasm and
can identify pretruncal nonaneurysmal hemorrhage 

5. CT can predict aneurysm location based on the pattern of blood in ≈ 78% of cases (but mostly for
MCA and A-comm aneurysms)

a) blood predominantly in anterior interhemispheric fissure (±blood in lateral ventricles)or
within the gyrus rectus suggests a-comm aneurysm

b) blood predominantly in Sylvian fissure is compatible with p-commor MCAaneurysm on
that side

c) blood predominantly in the prepontine or peduncular cistern suggests a basilar apex or SCA
aneurysm

d) blood predominantly within ventricles

● blood primarily in 4th and third ventricle: suggests lower posterior fossa source, such as PICA aneurysm or VA dissection

● blood primarily in the 3rd ventricle suggests a basilar apex aneurysm

6. with multiple aneurysms, CT may help identify which one bled by the location of blood 
----
{{:pasted:20240104-115902.png?400}}

Extensive [[subarachnoid hemorrhage]] distributed throughout [[perimesencephalic cistern]]s (predominantly in the [[chiasmatic cistern]]), [[prepontine cistern]], both [[Sylvian fissure]]s, and [[interhemispheric fissure]], with a component of bifrontal parasagittal [[intraparenchymal hematoma]] with mild adjacent [[vasogenic edema]]. The hemorrhage also extends into the [[ventricular system]] ([[third ventricle]] and [[lateral ventricle]]s). Findings consistent with modified Fisher grade IV subarachnoid hemorrhage.

This extension is compatible with an [[aneurysmal subarachnoid hemorrhage]] pattern.

Erasure of cerebral [[sulci]], predominantly frontotemporal, in relation to diffuse [[cerebral edema]].

Increased ventricular size for the patient's age.
----

----


In the early phase, during the first 24 hours, [[Head computed tomography ]], combined with intracranial CT angiography is recommended to make a positive diagnosis of subarachnoid hemorrhage (SAH), to identify the cause and to investigate for an [[intracranial aneurysm]]. Cerebral MRI may be proposed if the patient's clinical condition allows it. [[FLAIR]] imaging is more sensitive than CT to demonstrate a subarachnoid hemorrhage and offers greater degrees of sensitivity for the diagnosis of restricted subarachnoid hemorrhage in cortical sulcus. A lumbar puncture should be performed if these investigations are normal while clinical suspicion is high
((Edjlali M, Rodriguez-Régent C, Hodel J, Aboukais R, Trystram D, Pruvo JP,
Meder JF, Oppenheim C, Lejeune JP, Leclerc X, Naggara O. Subarachnoid hemorrhage 
in ten questions. Diagn Interv Imaging. 2015 Jul-Aug;96(7-8):657-66. doi:
10.1016/j.diii.2015.06.003. Epub 2015 Jul 2. PubMed PMID: 26141485.
)).

Noncontrast computed tomography is highly sensitive in detecting subarachnoid blood, especially within 6 hours of haemorrhage.

The distribution of the subarachnoid blood as shown on the first CT scan after aneurysm rupture barely allows to predict the symptomatic aneurysm site. Thus, neurosurgical decision making (identification of the ruptured aneurysm in patients with multiple aneurysms; surgical exploration in patients with non-perimesencephal SAH, but negative angiography) should not rely on the first CT scan after SAH
((Rohde V, Mayfrank L, Bertalanffy H, Mull M, Gilsbach JM. [Aneurysmal
subarachnoid hemorrhage: role of computerized tomography for correct prediction
of the ruptured aneurysm site]. Zentralbl Neurochir. 2003;64(3):116-22. German.
PubMed PMID: 12975746.)).

Rogers et al. report significant differences in the diagnostic approach of Australasian emergency physicians and trainees to this condition, in particular the utility of CT within 6 h for exclusion of SAH
((Rogers A, Furyk J, Banks C, Chu K. Diagnosis of subarachnoid haemorrhage: a
survey of Australasian emergency physicians and trainees. Emerg Med Australas.
2014 Oct;26(5):468-73. doi: 10.1111/1742-6723.12284. Epub 2014 Sep 3. PubMed
PMID: 25186282.
)).

===== Volume =====
The amount of blood in cisterns and fissures: important prognosticator for vasospasm.
----
Accurate volumetric assessment of spontaneous [[aneurysmal subarachnoid hemorrhage]] (aSAH) is a labor-intensive [[task]] performed with current manual and semiautomatic methods that might be relevant for its clinical and prognostic implications. 
In a research, García-García et al. sought to develop and validate an artificial intelligence-driven, fully automated blood [[segmentation]] tool for SAH patients via non-contrast computed tomography (NCCT) scans employing a transformer-based Swin-UNETR architecture.

They retrospectively analyzed NCCT scans from patients with confirmed aSAH utilizing the Swin-UNETR for segmentation. The performance of the proposed method was evaluated against manually segmented ground truth data using metrics such as Dice score, Intersection over Union (IoU), Volumetric Similarity Index(VSI), Symmetric Average Surface Distance(SASD), Sensitivity and Specificity. A validation cohort from an external institution was included to test the generalizability of the model.

The model demonstrated high accuracy with robust performance metrics across the internal and [[external validation]] cohorts. Notably, it achieved high Dice coefficient (0.873±0.097), IoU (0.810±0.092), VSI (0.840±0.131), Sensitivity (0.821±0.217) and Specificity (0.996±0.004) values and a low SASD (1.866±2.910), suggesting proficiency in segmenting blood in SAH patients. The model's efficiency was reflected in its processing speed, indicating potential for real-time applications.

The Swin UNETR-based model offers significant advances in the automated segmentation of blood in SAH patients on NCCT images. Despite the computational demands, the model operates effectively on standard hardware with a user-friendly interface, facilitating broader clinical adoption. Further validation across diverse datasets is warranted to confirm its clinical reliability
((García-García S, Cepeda S, Arrese I, Sarabia R. A Fully Automated Pipeline Using Swin Transformers for Deep Learning-Based Blood Segmentation on Head CT Scans After Aneurysmal Subarachnoid Hemorrhage. World Neurosurg. 2024 Aug 5:S1878-8750(24)01357-3. doi: 10.1016/j.wneu.2024.07.216. Epub ahead of print. PMID: 39111661.))