Clinical and Radiological Co-relation of Posterior Circulation Stroke in a Tertiary Care Centre in Southern IndiaCorrespondence Address :
Dr. Kora S.A.
Shailaja Nilaya, Mahaveer Road
Bagalkot- 587 101, Karnataka, India
Aim & Introduction: The present study has been undertaken at a tertiary care centre in rural India to know about the Clinical and Radiological (CT Scan) co-relation of Posterior Circulation Stroke as CT Scan is cheaper, easily available and faster compared to MRI.
Material And Methods: A total number of 25 cases were studied during the period from Jan 2010 to Dec 2010, from among those who were admitted to department of Medicine and Neurology in S.Nijalingappa Medical College and HSK Hospital & Research Center. Detailed clinical history was taken in all patients with general physical examination, CBC, urine analysis, random blood sugar,blood urea, serum electrolytes, lipid profile, ECG, CXR, and CT scan were done. In some selected cases CSF analysis, EEG and ECHO were done.
Results & Conclusion: Infra tentorial infarcts (83.3%) were seen more frequently than supra tentorial infarcts (16.6%) in this study. CT scan was 100% positive in supra tentorial ischemic strokes and in both infra & supra tentorial hemorrhage. CT scan was only 43% positive in cases of infra tentorial ischemic infarct especially in brain stem infarct. To summarize we recommend CT scan is the first option in critically ill, poor rural Indian population.
Posterior circulation strokes, CT scan positivity, Infratentorial, Supratentorial
The area of brain stem, cerebellum, occipital lobes and thalamus is supplied by two vertebral arteries, one basilar artery and two posterior cerebral arteries (1). This circulation is called posterior circulation. The incidence of strokes in posterior circulation is about 10 to 15 % (2).
The Posterior circulation strokes ranges from fluctuating brainstem symptoms, multiple cranial palsies, cerebellar signs and visual disturbances to many syndromes like lateral medullary, medial medullary, locked in to top of basilar syndrome (3). Many a times it mimics like anterior circulation strokes (4).
Brain imaging became possible in 1970 after introduction of computed tomography (CT) by Godfrey Hounsfield. CT proved useful for posterior circulation hemorrhage (5). Magnetic resonance imaging (MRI) introduced in 1980â€™s, permitted far superior imaging of brainstem and cerebellar infarcts (6),(7). Newer generation CT scans reveals cerebellar, posterior cerebral hemisphere and brain stem softenings. Cerebellar and pontine hemorrhages are almost always visible on CT.
The limited value of CT Scans for detecting ischemic lesions in the posterior fossa is related to the smaller size lesion (less than 2 cm) which are usually missed (8) and to the bone artifacts produced by sections through petrous bone. CT scan cannot precisely relate an infarct to a particular vertebrobasilar branch because of arterial distribution and extensive anastomoses (9).
CT appearances of the brainstem and cerebellar infarcts show 3 different stages.
(a) Acute stage (1 to 5 days): It causes low density in un-enhanced CT scan due to increased water content.(b) Subacute stage (6 days to 3 weeks): It reveals a lesion of lower density or isodensity with less mass effect. Abundant neutral fats from myelin breakdown contained in microglia and phagocytes are responsible for this hypodensity. Isodensity in this stage is known as â€śfogging effectâ€ť. Exact mechanism of this effect is not known. Some believe that this is due to capillary dilatation and the extravasation of macrophages. But this isodensity becomes hyperdense after contrast enhancement. (b) Chronic stage (3 weeks or more): Cystic space filled with fluid of density similar to cerebrospinal fluid replaces the parenchyma as well defined areas of low density.
Various studies showed that only 50% to 60% of clinical diagnosed brain stem infarcts show consistent CT changes. Hemorrhagic infarctions are areas of increased density (40-90 HU) with indistinct margins, mottled appearance with little mass effect. Hemorrhages in posterior circulation are always picked by CT scan. Aneurysms of basilar artery are visualized on CT scan after enhancement in around 60% to 70% of cases. CT scan also helps in detecting AVM on contrast enhancement. Another usefulness of CT scan in posterior circulation strokes is to detect hydrocephalus which will be helpful in patient management.
This study was done to know the positivity of CT scan in posterior circulation strokes. Though MRI is the best tool but it is not widely available in this part of India (9). CT scan is inexpensive and very useful in critically ill patients as it requires less time.
Hence we have decided to study incidence, types, distribution of lesions CT wise and the clinical and radiological (CT scan) corelation in posterior circulation strokes.
This study was conducted during the period from Jan 2010 to Dec 2010. During this period all posterior circulation strokes admitted to Neurology and Medicine departments of S.Nijalingappa Medical College and HSK Hospital & Research Centre were studied. This study consisted of total 25 posterior circulation strokes.
All posterior circulation strokes were included during the study period. The diagnosis of posterior circulation was made when the patient had a clinical stroke syndrome compatible with involvement of posterior circulation territory with the help of clinical signs and symptoms and by means of classical syndromes like Claudeâ€™s, Weberâ€™s, Balintâ€™s, Lateral medullary, Medial medullary, Locked in and top of basilar syndromes (3).
If CT scan showed recent infarction, haemorrhage in the anterior circulation and other non-vascular lesions and then they were excluded from the study sample.
A detailed history was obtained from the patient or a close relative regarding the onset of stroke, risk factors and family history.A detailed physical examination was done according to the proforma including vital signs and detailed examination of other systems. Optic fundus was examined in all the cases.
All the patients were investigated for CBC, ESR, urine analysis, random blood sugar, blood urea, serum electrolytes, lipid profile, RA factor, VDRL, ECG and chest radiography. CT scan was done in all patients in the study whenever needed. CSF, EEG & ECHO was done.
OBSERVATION & RESULTS
In posterior circulation strokes, Infratentorial stroke was common in both ischemic and hemorrhagic strokes. They constituted 52.6 and 83.3% respectively.
The incidence of infratentorial lesion was more (83%) compared to supratentorial lesion (16%) in haemorrhagic strokes but both have an equal incidence (40% each) in case of ischemic strokes. Inischemic stroke, incidence of occipital stroke (33.3%) was highest followed by cerebellar strokes (26.6%). In hemorrhagic strokes, highest incidence was of pontine hemorrhage (50%) followed by cerebellar hemorrhage (33%).
CT scan positivity was 100% in the hemorrhagic strokes but in ischemic infratentorial lesion excluding cerebellum its positivity was 43%.
Twenty five cases of posterior circulation strokes admitted to Medicine and Neurology wards of HSK Hospital & Research Center during period of 12 months (From Jan 2010 to Dec 2010) were studied for incidence, types, distribution of lesions CT wise and CT Scan positivity. The incidence of posterior circulation stroke was 12.3% in the study, which was comparable with other studies conducted by Jones.et al(10). (11) (17%) and Richard et al (2) (14.8%).
Incidence of infratentorial ischemic strokes was high (53%) compared to other sites in the present study. But the incidence of infratentorial strokes was less compared to Bogousslavsky et al study (12). This can be explained on the basis that in our study we used only CT scan to identify infratentorial lesion which is a poor diagnostic tool compared to MRI (9) and magnetic resonance angiography which was used in their study (13),(14).
CT scan positivity in the present study correlates well with the other studies (15). This low sensitivity of CT scan is due to bony artifacts interference, computer ripple (â€śover shootâ€ť) artifacts and partial volume effects. The limited value of CT Scans for detecting ischemic lesions in the posterior fossa is related to the smaller size lesion (less than 2 cm) which are usually missed (8) The low positivityof CT scan is for only ischemic infratentorial lesion excluding cerebellum where it is 100% positive. Cerebellar detection in the present study is 100 %.Both supra & infra tentorial hemorrhages are always detected by CT scan and same in this study also. For detecting hemorrhagic, ischemic supra tentorial and cerebellar infracts CT scan is good.
Principle uses of CT scan in posterior circulation strokes are:
(a) To separate brainstem and cerebellar hemorrhage from occlusive diseases. (b) To establish cerebellar infarction and posterior fossa pressure. (c) To determine the presence and distribution of distal basilar artery infarction (occipital and temporal lobe) in patients with symptoms of brain stem ischemia. (d) To visualize basilar artery aneurysm.
Hence we conclude still CT scan is first option in critically ill, poor rural Indian population.
The authors wish to thank Dr. Ashok Mallapur, Principal, S. Nijalingappa Medical College for his guidance during this study.
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