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 Table of Contents    
ORIGINAL ARTICLE  
Year : 2015  |  Volume : 8  |  Issue : 2  |  Page : 77-82
Incidental cranial CT findings in head injury patients in a Nigerian tertiary hospital


1 Department of Radiology, Division of Neurological Surgery, Neurology Unit, College of Medicine, University of Ibadan; Department of Radiology, University College Hospital, Ibadan, Nigeria
2 Department of Surgery, Division of Neurological Surgery, Neurology Unit, College of Medicine, University of Ibadan, Ibadan, Nigeria
3 Department of Medicine, Neurology Unit, College of Medicine, University of Ibadan, Ibadan, Nigeria
4 Department of Radiology, University College Hospital, Ibadan, Nigeria

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Date of Submission18-Nov-2013
Date of Acceptance18-Jul-2014
Date of Web Publication21-Apr-2015
 

   Abstract 

Background: Incidental findings on computed tomography (CT) scans are occasionally noted in patients presenting with head injury. Since it can be assumed that head injured patients are of normal health status before the accident, these findings may be a representation of their frequency in the general population. Our aim was to determine the prevalence of such incidental findings among head injured patients in Nigeria's foremost center of clinical neurosciences. Materials and Methods: We conducted a retrospective review of CT scan images of 591 consecutive eligible patients over a 5-year period (2006-2010) to identify incidental findings. The images were evaluated by consensus agreement of two radiologists. Associations with gender and age were explored using appropriate statistical tests with an alpha level of 0.05. Results: The mean patient age was 34.6 ± 21.2 years, and male to female ratio was 3.2: 1. Incidental findings were noted in 503/591 (85.1 %) of the scans. Intracranial calcification was the commonest finding occurring in 61.8% of patients. Over 90% of the findings were benign. Compared with older ones, patients under the age of 60 were less likely, (P < 0.001), to have incidental findings. Conclusion: Although the majority of incidental findings in this African cohort of head injury patients are benign some clinically significant lesions were detectable. It is therefore recommended that such findings be adequately described in the radiological reports for proper counseling and follow-up.

Keywords: Computed tomography, incidental finding, head injury

How to cite this article:
Ogbole GI, Adeleye AO, Owolabi MO, Olatunji RB, Yusuf BP. Incidental cranial CT findings in head injury patients in a Nigerian tertiary hospital. J Emerg Trauma Shock 2015;8:77-82

How to cite this URL:
Ogbole GI, Adeleye AO, Owolabi MO, Olatunji RB, Yusuf BP. Incidental cranial CT findings in head injury patients in a Nigerian tertiary hospital. J Emerg Trauma Shock [serial online] 2015 [cited 2019 Jul 21];8:77-82. Available from: http://www.onlinejets.org/text.asp?2015/8/2/77/155499



   Introduction Top


Computed tomography (CT) scanning is increasingly used both in research and in clinical medicine in Nigeria, and the quality of images obtained with newer helical scanners is continually being improved upon. [1],[2],[3],[4],[5] The accessibility of CT scanners to Nigerian head injury patients has increased over the years. [3],[4],[5] With these increases, the detection of unexpected, apparently asymptomatic brain abnormalities such as brain tumors, calcifications, anatomical variants, cysts, aneurysms and some other subclinical vascular pathologic changes become possible. These findings are frequently included in the radiology report are usually unrelated to the principal complaint and may not be pertinent to the immediate care of the patient. Such unexpected abnormalities are classified as "incidental findings".

Relatively few studies have reported incidental findings in head injury, most reports on incidental CT findings have focused on intracranial tumors and conditions requiring follow-up or intervention and to our knowledge there is none in an African setting. [6],[7],[8],[9],[10] With the diagnostic sensitivity of CT and robust reporting by radiologists, more incidental lesions are likely to be seen. While most of these incidental findings are benign and require no follow-up, there are a few whose discovery may hold unexpected importance to the patient's future well-being. The latter may therefore require serial imaging follow-up and close supervision of the patients by their primary care physicians. [7],[8],[9],[10] Also, identification and reporting of these mostly innocuous findings creates the need for clinicians to properly interpret them and communicate the import to patients.

The assessment of the true prevalence of incidental cranial CT scan findings in the general population is logistically difficult in our low-resource practice area. We therefore assumed that head-injured patients whose only clinical indication for their neuroimaging was the index trauma would be somewhat representative of the general population. [11]

The purpose of this study was to assess the frequency of these incidental findings detected in head-injured patients after a cranial CT scan in our center.


   Materials and Methods Top


Cranial CT scans of 591 head trauma patients obtained from 2006-2010 were retrospectively evaluated by 2 radiologists (GIO and OAO) for recognized incidental findings. The CT scans were performed within one week of the event on a GE Brightspeed S (GE medical systems, USA) CT scanner. All cranial CT scans included 15-25 sections (each slice being 3 mm thick at the skull base and 7 mm thick from the base to the vertex). At our center the routine cranial axial CT scan for head trauma was usually performed at approximately 20° tilt relative to the orbitomeatal line. We excluded those CT scans/images that were not standard or were of poor image quality. [11]

Classification of incidental findings

All findings and classifications were derived by consensus agreement of the two radiologists. We replicated some of the methods used in previous studies. [9],[10],[11] With these, our own findings were classified into one of two categories:

  1. Benign/(not clinically significant): No clinical follow up necessary, common normal findings in asymptomatic subjects (class 1: Minimal paranasal sinus disease, falx/pineal calcifications)
  2. Clinically significant: Routine or urgent follow-up necessary (class 2: Acute sinusitis, non-acute intraparenchymal or extra-axial lesions other than small white matter foci and, acute intracranial lesions with significant mass effect).


Statistical analysis

We calculated the prevalence of each incidental brain finding in the study population. In reporting the prevalence, multiple similar findings within one patient (e.g., more than one sinus abnormality or multiple asymptomatic brain infarcts) were counted as a single incidental finding.

Next, we calculated the age-specific prevalence rates of the most frequent incidental findings. For intracranial calcifications, we calculated the age-specific median and interquartile range.

We used student t-test to achieve a comparison of the mean age of patients with and without incidental findings.

Other statistical evidence of associations on categorical variables were computed from Chi-square tests of contingency. A P-value of <0.05 was considered as significant.


   Results Top


Of the 636 scans evaluated, 591 (84.9%) scans had complete and eligible data for review. We detected incidental findings in 85.1% (503/591) patients but the majority of these, 462/503 (80.7%) were innocuous, findings requiring no clinical follow-up (class 1 findings as defined in 'Methods', above).

Findings classified to have required follow-up (class 2) were 41 in all (8.2% of the incidental findings, or, 6.5% of all CT images). These included, intracranial tumours/lesions, skull lesions and acute sinus or mastoid disease.

The ages of patients evaluated ranged from a few days of life to 95 years, mean 35.6 ± 21.2 years. The mean age of patients with incidental findings (39.0 years ± SD) was significantly higher than those without (16.2 years ± SD, P = 0.0001). Children below the age of 18 years constituted 19.4% of the cohort examined. Overall there were more males (72.1%) than females (27.9%) giving an approximate male to female ratio of 3.2:1. The head injury was caused by road traffic accidents (RTA) in 65.6% of the cases, fall from height in 20.0% assault in 13% and other causes accounted for 1.4%.

In all, we noted 11 kinds of structural incidental findings [Table 1]. The commonest was intracranial calcification (67.7%) followed by sinusitis/sinus abnormalities (52.8%). Leucomalacia was the least common incidental finding, seen in only seven patients (1.2%).
Table 1: Distribution of incidental findings in head injured patients

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The other incidental findings were 4 intracranial tumors which included a suspected meningioma, giant cell astrocytoma associated with tuberous sclerosis [Figure 1], pituitary apoplexy, and suspected tuberculoma [Figure 2]. Other findings are listed in [Table 1].
Figure 1: Axial Cranial CT images of a 32-year-old head injured patient with incidentally discovered tuberous sclerosis. Non contrast enhanced images (a) show an isodense mass in the anterior horn of the left lateral ventricle with calcifications within it (arrow). Hemorrhage within the posterior horn of the lateral ventricles is also noted. (b) Subependymal calcifications noted at body of the lateral ventricles. Follow-up CT images (c and d) show avid near-homogenous contrast enhancement

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Figure 2: Axial non-contrast cranial CT in a 70-year-old female with severe head injury showing acute intracerebral haemorrhage and subdural collection in the left fronto-parietal region with significant midline shift. An incidental finding of a fairly rounded calcified mass is found adjacent to the parietal bone suspected to be a tuberculoma

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Ventriculomegaly, cerebral atrophy, Dandy Walker variant, intracranial calcification, Sinusitis, infarction, skull lesion, collection and mastoid opacity/sclerosis were all significantly commoner in the adult population (P < 0.05). Suspected physiological calcification of the globus pallidus was visualized in 53 patients (10%). The frequency of these visualizations increased with increasing age.


   Discussion Top


Our findings demonstrate the prevalence of incidental findings on CT in head-injured patients in a major referral centre in Nigeria. The prevalence of incidental findings on neuroimaging of the head in the literature are as varied as the imaging modality used; technique of image acquisition; demographic and ethno-racial characteristic\s of subjects; as well as case definition of incidental findings reported. Cranial CT based studies reported prevalences which range from as low as 1% to as high as 19%. [9],[10],[11],[12],[13],[14] The prevalence in our series is 85.1% which is high when compared with the previous CT based studies, though majority of our findings was innocuous, non-critical and without need of further investigation or clinical follow up. An intermediate prevalence of 47% was however reported in one magnetic resonance imaging (MRI) based study. [6]

The spectra and prevalence of reported incidental findings are diverse. In this series, calcification (61.8%) was the most frequent incidental finding followed by sinusitis (52.8%), mastoid opacity/sclerosis (32.1%), brain atrophy (16.9%) and arachnoid cysts (9.8%). Calcification was however, either an infrequent finding or not even considered in some previous studies. [9],[10],[11],[12],[13],[14]

The relatively young mean age of our cohort is similar to those of most other CT based studies and is unlikely to account for the observed disparity in frequency of calcification reported.

Although MRI based series had relatively older participants, [6],[15] calcification may be difficult to detect due to the low sensitivity of MRI for calcifications and this may explain the lower prevalence reported by Katzman et al. [16] This observation suggests that intracranial calcification develops at an earlier age in black Africans than other races. Further studies will however be necessary to verify this.

The low frequency of incidental finding of intracranial calcifications in previous studies may also be because of the different classification methods used. For example, Bordignon and Arruda [10] classified calcifications into three different groups of; one calcification (38.95%), several calcifications (17.6%) and basal ganglia calcification (5.62%). This form of grouping was very nonspecific and provides little information about location and the brain tissue involved. Brain atrophy was their most common incidental finding.

Eskandary et al., seem to only consider pineal calcification and basal ganglia calcification. We considered all forms of intracranial calcifications including falcine calcification which occurs in about 10% of elderly population. [17] In view of the high percentage of calcifications we found, there might be a higher prevalence of intracranial calcification among black Africans, a hypothesis that may require further study. The calcifications we established occurred significantly in the older age-group, especially basal ganglia calcifications (P = < 0.001). They were mainly benign and do not require further clinical follow-up [Table 2].
Table 2: Association of age with the incidental findings on CT

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The calcifications which could be considered pathological were those found in a patient suspected to have sub-ependymal giant cell astrocytoma and the calcified cortical tubers which were seen in the patient were indicative of tuberous sclerosis. Although asymptomatic prior to his head injury, this patient will require follow up and possible intervention.

Sinusitis and mastoid disease formed the second and third most common incidental findings in our series. This probably reflects the higher incidence of infections in a developing country like Nigeria. Bordignon and Arruda [10] found a relatively low prevalence of sinus disease (4.49%) compared with the 52.8% we recorded in our series. The Nigerian climate found in our work. Eskandary et al., [11] did not report any case of sinus or mastoid disease.

Our series clearly demonstrated brain atrophy, hydrocephalus ex vacuo, leucomalacia, infarct, and mastoid opacity to be age-related [Table 2]. [Table 3] clearly showed the gender related discrepancy with CT findings of atrophy, calcifications, sinusitis and cerebral infarctions in males.
Table 3: Association of gender with incidental findings on CT

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Brain tumors are important incidental findings and autopsy reveals the frequency of between 1% and 2%. [14] We found 4 (0.7%) cases of suspected brain neoplasms. Most incidental findings of intracranial lesions have focused on pituitary adenoma. [18],[19],[20] We only found one case of pituitary adenoma presenting as pituitary apoplexy. The other tumors we found were suspected meningioma, tuberous sclerosis and tuberculoma. Meningioma is the most common of all incidental tumors accounting for up to 33% of the incidental tumors found at autopsy. [21]

Intracranial arachnoid cysts are often also discovered as incidental finding on imaging and make up 0.4-1% of the intracranial space occupying lesions. [22],[23] The incidence of arachnoid cysts [Figure 3] found in our study is comparatively higher than previous studies. [10],[11],[22],[23] This high proportion may be due to the difficulty in distinguishing between arachnoid cysts of the suprasellar region and other benign cysts resulting in an over call as the differential diagnosis may be wide and may include Rathke cyst, third ventricular dilatation, craniopharyngioma, or epidermoid tumors. [24] This imaging finding may require further investigation and validation from autopsy studies in our environment.
Figure 3: Arachnoid cyst (white arrow) in a 4-year-old boy who fell from height with associated parietal bone fracture (arrow head)

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Some forms of intracranial calcifications, tuberous sclerosis or tuberculomas may predispose to seizures which could be the cause of a road traffic accident or fall from height in the first place. Due to the retrospective nature of our study, the circumstances surrounding the cause of the head trauma could not be adequately established. However it is plausible that in those patients found with intracranial abnormalities, their injury may have resulted from a seizure event. Previous head trauma is also a possible etiological factor as head trauma victims are 12 times more likely than people who have not suffered from head injuries to have seizures. [25] Head injuries occur all the time. People who have had acute intracranial hematomas can also have a high rate of epilepsy.

A limitation of this study is a referral bias that predominantly involved more young males, who apparently are more likely to present with head injury. [26] However it is recognized that the Nigerian population is predominantly young with a life expectancy of 47 years and a greater proportion of males. [27]

Also, we do not routinely perform contrast CT examinations for trauma cases especially when acute intracranial hemorrhage is found. This may also limit the detection and number of contrast enhancing lesions. We did not review the patients chart for documentation of counseling, referral or follow-up of incidental findings thus we could not comment on patient's outcome.


   Conclusion Top


Most incidental findings are benign and non-critical. However, we recommend that such findings be included in the radiological reports for proper counseling and follow-up when required.

 
   References Top

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Correspondence Address:
Dr. Godwin I Ogbole
Department of Radiology, Division of Neurological Surgery, Neurology Unit, College of Medicine, University of Ibadan; Department of Radiology, University College Hospital, Ibadan
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0974-2700.155499

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