ORIGINAL ARTICLE
Year : 2020 | Volume
: 69 | Issue : 2 | Page : 67--70
Radiological study of the adipose tissue at the para-cavernous region of middle cranial fossa
PV Santosh Rai1, Anees Dudekula1, Anand Venugopal1, BV Murlimanju2, Muralidhar Pai3, Sampath Madhyastha4,
1 Department of Radiodiagnosis, Kasturba Medical College and Hospital, Mangalore, Manipal Academy of Higher Education, Karnataka, India
2 Department of Anatomy, Kasturba Medical College, Mangalore, Manipal Academy of Higher Education, Karnataka, India
3 Department of Neurosurgery, Kasturba Medical College, Mangalore, Manipal Academy of Higher Education, Karnataka, India
4 Department of Anatomy, Faculty of Medicine, Kuwait University, Kuwait City, Kuwait
Correspondence Address:
Dr. B V Murlimanju
Department of Anatomy, Kasturba Medical College, Mangalore - 575 001, Karnataka
India
Abstract
Introduction: The cavernous sinus (CS) lesions are difficult to identify on computed tomogram (CT) film, and the subtle changes may help in the diagnosis. The objective of the present study was to examine the para-cavernous adipose tissue in the CT scan in the Indian population. Material and Methods: The study included 100 patients of all age groups, who were examined using a 16 slice multidetector CT. The axial images were analyzed for the presence of adipose tissue on either side of the CS. The intracranial pathology and atrophic changes, if any, were noted. Results: The present study observed that 17% of the patients had intracranial pathologies. Among the 83% of patients with no pathology, paracavernous adipose tissue was observed in 85.5% and 89.2% over the right and left sides, respectively. It was observed that the paracavernous fat was visualized in higher frequency in elderly adults. It was visualized in all the patients (100%) of over 60 years. In some patients, with mass effect, the paracavernous fat was obliterated over the ipsilateral side, but it was visualized on the contralateral side. Discussion and Conclusion: The present study suggests that the CS lesions are difficult to identify on the CT scan, and the subtle signs may help in making a diagnosis. The para-CS adipose deposit is one among these subtle changes; if there is the presence of adipose tissue on one side and its absence on the other side, then pathology should be suspected.
How to cite this article:
Santosh Rai P V, Dudekula A, Venugopal A, Murlimanju B V, Pai M, Madhyastha S. Radiological study of the adipose tissue at the para-cavernous region of middle cranial fossa.J Anat Soc India 2020;69:67-70
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How to cite this URL:
Santosh Rai P V, Dudekula A, Venugopal A, Murlimanju B V, Pai M, Madhyastha S. Radiological study of the adipose tissue at the para-cavernous region of middle cranial fossa. J Anat Soc India [serial online] 2020 [cited 2023 Mar 24 ];69:67-70
Available from: https://www.jasi.org.in/text.asp?2020/69/2/67/288677 |
Full Text
Introduction
Neurosurgeons, radiologists, ophthalmologists, and anatomists are studying the cavernous sinus (CS), and it is the venous structure, which lies one on either side of the hypophyseal fossa. CS has the internal carotid artery (ICA) and cranial nerves in it.[1] CS extends from the superior orbital fissure until the dorsum sellae.[2] The CS receives the drainage of veins of orbit, and CS itself will drain into the petrosal sinuses.[3] The CS communicates with pterygoid venous plexus through an emissary vein. It receives the superficial middle cerebral vein, and central vein of the retina. The ICA passes medially within the CS, and the abducent nerve (sixth cranial nerve) is present in the middle of the CS inferolateral to the ICA. The oculomotor (III), trochlear (IV), ophthalmic (V1), and maxillary (V2) division of trigeminal nerves are located at the lateral wall of the CS.[4] The maxillary nerve enters the foramen rotundum after leaving the CS. The ophthalmic nerve is found in the entire lateral wall of the CS and it goes toward the superior orbital fissure.[2]
The CS is posteriorly related to the trigeminal ganglion, which is covered by a fold of dura mater known as Meckel's cave. The infratemporal fossa lies inferior to CS, and it is connected through the foramen ovale. The foramen rotundum connects the CS with the pterygopalatine fossa. Since many important vessels and nerves pass through these foramina and openings, any pathological changes in the adjacent locations can spread to the CS through these openings.[5] It is also true that the CS thrombus can compress the surrounding structures. The CS syndrome is because of the space-occupying lesions, infective diseases, vascular lesions, and inflammations.[6] The orbital congestion, proptosis, sensory loss in the face, sympathetic imbalance, and ophthalmoplegia are the clinical features of the CS syndrome.[2]
The CS pathology may be missed during the routine computed tomogram (CT) examination, and magnetic resonance imaging (MRI) is considered as the best investigation by the radiologists. Under some circumstances, the CT scan is still advised because of some other reasons. In these situations, it is believed that the subtle changes around the CS will play a key role in suspecting the pathology. The CS may contain fatty deposits, which are considered as normal findings. The margins of the fissures and openings of the parasellar region at the middle cranial fossa are also surrounded by the adipose tissue deposits.[7] The absence of the adipose tissue is not considered as abnormal either,[8] however some lesions tend to widen the CS, causing obliteration of the adipose tissue at the parasellar region. The literature search revealed that there are not many studies available about the paracavernous adipose tissue in the Indian population.
Aims and objectives
The objective of the present investigation was to radiologically examine the adipose tissue in the paracavernous region in the Indian population.
Material and Methods
The present study included 100 consecutive patients of all age groups, who were examined using a 16 slice multidetector CT. Among them, 50 each was male and female patients. The CT examination of the head was performed with 5-mm slice thickness using the helical scanning technique in the axial plane, which was later reconstructed into 0.625-mm slice thickness images. Each image was observed for the presence of paracavernous fat on either side of the CS. Any intracranial pathology, if present, was noted. The atrophic changes in elderly patients were also noted.
Results
The present study observed that 17 (17%) of the patients had intracranial pathologies. The intracranial pathology included hemorrhage, infarction, and space-occupying lesions. The remaining 83 patients (83%) had no obvious pathology, except few elderly patients who had their age-related atrophic changes. Among these 83% of patients with no pathology, the paracavernous adipose tissue was observed in 85.5% (71 patients) and 89.2% (74 patients) over the right and left sides, respectively. In the rest of these patients, there was no discernible Parasellar Fat.
It was observed that paracavernous fat was visualized in higher frequency in adults with increasing age [Figure 1], and it was least visualized in the pediatric age group. In the age group of 1–10 years, only 1 among 5 patients (20%) presented with paracavernous fat, however after the age of 60 years, it was visualized in all the patients (100%) [Figure 1]. The frequency of visualization of paracavernous adipose tissue in the CT examination of various age groups in the present study is represented in [Figure 1]. The present study observed no gender-based discrimination in the visualization of paracavernous adipose deposits. In 3 of the patients (3%), the paracavernous fat was observed unilaterally, and there was no pathology observed even on detailed radiological examination on both sides. This CT observation is suggestive of asymmetrical adipose tissue.{Figure 1}
Among the 17 patients (17%) who had intracranial pathologies, the adipose tissue at the para sellar region was still visualized in a few of them. The paracavernous adipose tissue was observed in both right and left sides in 5 patients (28%). It was observed that these patients had intracranial lesion, which was not causing the mass effect. In few of the patients, with mass effect like uncal herniation due to large intracerebral bleed, huge infarct, space-occupying lesion, etc., the paracavernous adipose tissue was obliterated on the ipsilateral side, but the contralateral side paracavernous fat was always visualized. The paracavernous adipose tissue was visualized only on the right side in 6 patients (36%) and only on the left side in the remaining 6 patients (36%). These CT observations suggest that the intracranial pathology has no correlation with the presence or absence of paracavernous adipose tissue. Further the paracavernous fat was asymmetrical.
[Figure 2] shows the axial CT image of a patient in the present study, which visualized the normal para-cavernous adipose tissue on the right side [double white arrows in [Figure 2] and the obliteration of the adipose tissue on the left side [solitary black arrow in [Figure 2]. The T2 weighted MRI image of the same patient has confirmed the extra-axial lesion at the left paracavernous region [solitary white arrow in [Figure 3], which was histopathologically confirmed as the meningioma.{Figure 2}{Figure 3}
Discussion
The MRI is the investigation of choice if the CS pathologies are suspected.[9] However, many patients with CS lesions tend to present with nonspecific symptoms such as headaches or gradually diminishing vision. In such cases, the CT is the imaging modality, which is usually preferred taking the duration and cost factor into consideration. CT is also the preferred modality in oral and maxillo facial tumors to assess the tumor spread and bone involvement. The clinical history of one among our patients in the present study, an elderly gentleman, suggested that he presented to the hospital with the left orbital pain. He was also noted to have left third and fourth cranial nerve palsies. The proptosis was not observed over the left eye, and the ultrasound scan did not reveal any orbital or retro-orbital mass lesions. The plain CT of the head did not reveal any abnormality on the initial look. However, on the second look, there appeared to be an asymmetry of the adipose tissue, which is found lateral to the parasellar region. The para cavernous fat on the right side was distinctly visible, and there was the obliteration of the left para cavernous fat [Figure 2]. This gave us a clue to believe that the patient may have an underlying structural lesion. The MRI of the same patient revealed an extra-axial lesion at the left CS exactly at its lateral wall, which was apparent on the thin T2-weighted images [Figure 3]. The patient went for craniotomy and decompression by the neurosurgeon, and the tumor was sent for the histopathological examination. The histopathological report was that of meningioma.
The present study observed that the parasellar adipose tissue was very much obvious in elderly individuals [Figure 1]. This could be related to the occurrence of subtle brain atrophy as the age progresses. In some patients of the present study, the adipose tissue was observed only on one side. This adds a subtle clue to assess the level of mass effect on the CS in these patients. It is believed that the existence of fat in the parasellar space is important. The loss of adipose tissue around the superior orbital fissure is seen in orbital tumors spreading into the CS.[10] Whenever there is a perineural spread of tumor along the openings at the skull base, the obliteration of the fat at that opening is a subtle sign, which helps in assessing the extent of the tumor spread. Many CS pathologies such as CS hemangiomas or cavernous segment ICA aneurysm tend to expand the CS. The lesions which arise from the dura mater at the lateral wall of the CS like meningioma will expand the CS and make it appear bulkier. In these conditions, there is the loss of the adjacent fatty deposits, and the CS appears to lie in close approximation to the adjacent medial temporal lobe.[3]
The CS has no valves, which permits the blood to flow in both directions as per the requirement. The CS is prone to sepsis and thrombus formation because infection from multiple locations can reach it. CS has connections with the face and the infratemporal fossa. The inflammations at the sphenoid and ethmoid sinuses are the most common source of CS infection, which may be complicated as cavernous venous thrombosis (CVT). The inflammations at “dangerous area” of face, nasal cavity, tonsillitis, soft palate, dental caries, and otitis are not commonly leading to CS infection because of the widespread use of antibiotics.[11] The orbital inflammation very rarely cause CVT, although the CS drains the superior and inferior ophthalmic veins.[12] CS can also get involved in the malignancies; the carcinoma nasopharynx is the most common to metastasize into the CS through the skull base and the openings such as foramen rotundum, vidian canal, and foramen lacerum. However, it has been reported that the metastasis into the CS is rare.[3],[13] However, the metastasis can arise from renal, gastric, thyroid, bronchogenic, and breast malignancies. This can lead to the enlargement of the CS, lateral bulge of its peripheral part, and eventually would lead to the replacement of Meckel's cave with the connective tissue.[3],[13] The sphenoidal air sinus cancers would directly reach the CS by eroding the body of sphenoid.[3],[10]
It is described that 5% of all cases of ophthalmoplegia are due to the CS pathology. The etiologies can be grouped into thrombosis, aneurysms, fistulas, and tumors.[2] Meningioma is quite commonly seen in the CS. It can arise within the CS or from the surrounding meninges. The pituitary tumors can invade the CS easily as they are very closely related. They can involve either one side or both the side CS and the ophthalmoplegia will be associated with the endocrine imbalances. This can include acromegaly, galactorrhea or hypopituitarism. The pituitary tumors, invading the CS often present with unilateral or bilateral visual field defects.[2]
The Tolosa-Hunt syndrome is diagnosed by excluding the other causes of the cavernous syndrome. The etiologies such as infective, vascular, neoplastic, metabolic, traumatic, and inflammatory causes, have to be excluded. This syndrome is caused by a granulomatous inflammation or pseudo-tumor at the ventral part of the CS closer to the superior orbital fissure. The patients with this syndrome suffer from the retro-orbital pain along with the ophthalmoplegia with or without optic nerve involvement. The patient will be having a chronic history of symptoms with spontaneous remissions.[2]
Conclusion
After the examinations of the CT films in the present study and while making a diagnosis, we observed that the CS lesions are difficult to identify on CT film, and the subtle signs may aid in making a diagnosis. One among them is the obliteration of the para-CS adipose deposit. Even though the paracavernous adipose tissue is not seen in every individual, if there is the presence of adipose tissue on one side and its absence on the other side, the pathology of the CS should be suspected. The patient needs careful reassessment to localize the pathology and to make the correct diagnosis. We believe that the present study highlighted the subtle, hidden sign of this paracavernous adipose tissue in evaluating the CS lesions and as an indirect sign of the mass effect of the lesion.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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