You decide to repeat the angiogram 3 days later (Fig. 34.3).

After discussion with the neurointerventional team, you recommend a direct surgical approach of the lesion.

• Epicenter of hemorrhage anterior to the brainstem (interpeduncular and/or prepontine)
  
• There may be extension into the anterior part of the ambient cistern or the basal part of the sylvian fissure
  
• Absence of complete filling of the anterior interhemispheric fissure
  
• No more than minute amounts of blood in the lateral portion of the sylvian fissure
  
• Absence of frank intraventricular hemorrhage: Small amounts of blood sedimenting in the occipital horns of the lateral ventricle are permissible.1

• The CT has shown an aneurysmal SAH distribution and does not satisfy the criteria of pretruncal SAH mainly because of the filling of the sylvian and interhemispheric fissures. Accordingly, a ruptured intracranial aneurysm is not entirely excluded. Note the presence of moderate hydrocephalus. The initial management includes
  
  
  
  • Admission to intensive care unit
    
  • External ventricular drain (EVD) if there is progression of hydrocephalus or clinical deterioration
    
  • Bed rest and symptomatic treatment (e.g., analgesic, antiemetic)
    
  • Control of the blood pressure
    
  • Cardiac monitoring
    
  • Intravenous (IV) fluids: mild volume expansion and slight hemodilution
    
  • Calcium channel blockers: nimodipine
    
  • Laboratories: arterial blood gas (ABG), electrolytes, complete blood count (CBC), international normalized ratio (INR), partial thromboplastin time (PTT)
    
  • Seizure prophylaxis

• The right internal carotid injection reveals a small bulbous, broad-based dilatation at the anterior wall of the right internal carotid artery.
  
• This finding is compatible with the diagnosis of a ruptured blister-like internal carotid aneurysm. These aneurysms reportedly exhibit rapid growth and changes in shape as in this case.²

• Blister-like aneurysms are small sessile, hemispherical expansions at a nonbranching site of the anterior aspect of supraclinoid segment of the internal carotid artery (ICA).
  
• They are characterized by a very fragile wall and a poorly defined neck and are histologically distinct from saccular aneurysms.
  
• In relation to the ICA, they have been referred as
  
  
  
  • Dorsal
    
  • Distal-medial
    
  • Superior
    
  • Anterior wall1–4

• These aneurysms are associated with arteriosclerosis of the neighboring carotid wall.⁵
  
• Abrupt termination of the internal elastic lamina is seen at the border between the normal and sclerotic carotid wall.
  
• The dome is composed of fibrinous tissue and adventitia whereas the usual collagenous layer of saccular aneurysm is absent.
  
• Dissection and infiltration of the arterial wall by inflammatory cells is absent.
  
• Because of their very fragile walls and poorly defined necks, surgical exploration and clipping are very hazardous with a high rate of intraoperative or postoperative rupture.⁶

• Blister-like aneurysms have a high risk of intraoperative rupture with large lacerations of the ICA during clipping. These aneurysms require special consideration.

• Surgical strategies include^2,6–10
  
  
  
  • Opening of the sylvian fissure before accessing the carotid and chiasmatic cisterns
    
  • Frontal lobe retraction should be minimized and performed as late as possible because of adhesion of the frontal lobe to the aneurysm dome.
    
  • Clips should be applied while pressure within the ICA is low with temporary clipping of the ICA.
    
  • Clips’ blade should be applied parallel to the parent artery and should catch the arterial wall beyond the lesion.
    
  • Confirming the stability of clips is essential and is done with induced blood pressure elevation and repeated irrigation before closing the dura mater.
  
  
• Other potential surgical treatments
  
  
  
  • Wrapping the full circumference of the ICA and applying an encircling clip. Sundt clips can be used for wrapping because they allow encircling of the vessel with Dacron (Invista, Inc., Wichita, KS).
    
  • ICA trapping with or without bypass
    
  • Direct suturing
    
  • Stent placement, alone or with coiling, is increasingly being used or tested as a modality of treatment. It is based on the rationale of redirecting flow away from the dome. Long-term results are not available at present.
    
  • Bipolar coagulation has been used by some without documented long-term results.

• The prognosis is related to the clinical status on admission, evaluated by the Hunt and Hess clinical classification.
  
• However, because of the high incidence of intraoperative or postoperative bleeding, the prognosis is markedly worse than for those patients with saccular-type aneurysm.⁶