Abstract
We report a case of a 15-year-old Indian girl who presented with tinnitus, pain and ear discharge for one month and was preliminarily diagnosed with Chronic Suppurative Otitis Media (CSOM) with mastoiditis. She underwent a routine presurgical CT scan which revealed an aberrant vein, making it essential to exercise caution during surgery for CSOM. The aberrant vessel was identified as a Petrosquamous Sinus. A Petrosquamous Sinus is a persistent fetal vein that connects the transverse sinus with the retromandibular vein and may regress in an individual by birth. Its importance lies in the risk of haemorrhage it carries during otological surgeries. A Digital Subtraction Angiography proved to be a vital step in isolating the path of the vein for better visualisation of the course, thus giving a better idea about the anatomical relations of the vessel during the surgery. The tympanoplasty was performed with care to prevent damaging the vein. The patient had no complications in the postoperative period and made a quick recovery.
Keywords: Petrosquamous Sinus, Digital subtraction Angiography, CSOM, Tympanoplasty
Introduction
A Petrosquamous Sinus (PSS) is a persistent fetal vein usually absent in an individual at birth and commonly connects the lateral sinus with the retromandibular vein [1]. It is an emissary vein and is said to be more common in individuals with base of the skull abnormalities [2] In the study performed by Koeslinga et al., HRCTs were performed on 233 patients. Amongst these, only six cases of unilateral PSS were identified, with an incidence of 1% [3].
In their report, K. Marsot-Dupuch et al. described the course of the PSS as originating from the dorsolateral part of the transverse sinus right before meeting with the superior petrosal sinus. They describe how it traverses the lateral superior part of the petrous bone, draining into the retromandibular vein and the pterygoid venous plexus. After passing through the foramen retro articular, it meets the foramen ovale, respectively [1].
We report a case of a PSS that has complicated the surgical intervention meant to treat a patient of Chronic Suppurative Otitis Media.
Case History
A 15-year-old girl presented to us with tinnitus, pain and ear discharge for a month. An aberrant vessel was found incidentally during routine High resolution Computed Tomography (HRCT) investigations prior to the tympanoplasty for Chronic Suppurative Otitis Media (CSOM) and Mastoiditis. The patient had been largely asymptomatic with respect to the aberrant vessel but had tinnitus, which has been seen in other vascular anomalies.
The HRCT showed a posterior sulcus vein extending from the junction of the left transverse and sigmoid sinus connecting via emissary in the occipital bone with the extracranial venous system.
It also showed an anterior-left lateral PSS tract coursing anteriorly in the mastoid and petrous temporal bone, superior to the bony external auditory canal and left temporomandibular joint and ending through a foramen posterior to the left TMJ (foramen retroauriculare).
The HRCT also helped to visualise the suppurative lesion, which was depicted by the opacification of the left middle ear cavity and antrum. The remaining mastoid air cells on the left were sclerotic. An incidental pituitary macroadenoma was noted on the HRCT, which was unchanged from previous scans. The rest of the investigation showed no significant findings. Additionally, the Magnetic Resonance Imaging (MRI) investigation performed prior to the intervention corroborated the HRCT findings.
A Digital Subtraction Angiography (DSA) was done post-detection of the anomalous vessel (DSA) to better identify the vessel and its course. DSA confirmed the diagnosis made of it being a PSS. The course of the vein began from the left sigmoid sinus, traversed the roof of the mastoid air cells and external auditory canal anteriorly, reached anterior to the anterior wall of the external auditory canal and opened laterally into the subgaleal plane, anterior to the external auditory canal to continue with the superficial temporal vessels. It then went on to join the retromandibular vein, which drains into the external jugular vein.
The diagnosis of this rare phenomenon helped outline the surgical management for this case. Using DSA, the vessel was delineated and gave the surgical team a visual depiction of the course of the vein and a clear picture of what they would encounter during the surgery. This led to a well-informed plan of action to deal with the aberrant vessel in the case of any inadvertent venous injury during the surgical procedure. It also helped confirm the role of the emissary vein in the venous drainage of the patient’s brain (Figs. 1, 2, 3, 4 and 5).
Fig. 1.
CT post contrast axial images show a mastoid emissary vein (arrow in Fig. 1A) arising from the sigmoid sinus superiorly. It is reaching anterolaterally upto the middle cranial fossa abutting the anterior margin of the petrous temporal bone (star in Fig. 1C). It extends anterolaterally to reach the anterior wall of the external auditory canal (arrow in Fig. 1C) and is seen draining into tributaries of the external jugular vein (arrows in Fig. 1D and E). This represents the petrosquamous sinus
Fig. 2.
Coronal reformatted images of contrast enhanced CT imaging shows course of the emissary vein and its drainage into tributary of the external jugular vein (arrow in Fig. 2F)
Fig. 3.
MR venography images show an extra flow related signal adjacent to the left sigmoid sinus (star in Fig. 3A and block arrow in Fig. 3B) which is seen to drain into a tributary of the external jugular vein (arrow in Fig. 3D)
Fig. 4.
Cerebral DSA venous phase confirms the above findings. There is an emissary vein (shown by arrows) which is seen draining into the external jugular vein. Cerebral DSA is a valuable tool in demonstrating this anatomical variant and can act as a road map for temporal bone surgeries
Fig. 5.
Intraoperative image during the tympanoplasty procedure reveals the posterior relation of the Petrosquamous sinus with respect to the sclerotic mastoid cavity which correlates with the pre-op CT image
Clinical Management
The patient underwent a Left Cortical Mastoidectomy with Type 1 Tympanoplasty using a temporalis fascia graft. The emissary vein was observed in the posterior and superior boundary of the cortical mastoidectomy.
The dissection, i.e., Mastoid drilling, was done to clear the granulation in the mastoid antrum in a precise manner keeping in mind the previously delineated vein to ensure there was no damage to it and, at the same time, making sure the disease was cleared in its entirety.
The patient’s post-op was uneventful, and she had a quick recovery.
Discussion
A Petrosquamous sinus is an emissary vein that connects the intracranial and extracranial drainage networks and may have a small role to play in the drainage of the brain of healthy individuals but is hypothesised to play a more prominent role in the case of malformations of the skull base [1, 4].
It is said to be a remnant of the connection between the superficial layer and the middle layer of venous drainage that is present during the development of the foetus [1]. In adults, two pathways connect the cerebral veins to the jugular venous system, the first being from the drainage of the superficial and deep middle cerebral veins into the pterygoid venous plexus by the cavernous sinus and/or the emissary veins of the middle cranial fossa. The second pathway involves a path between the rostral portion of the transverse sinus and the veins of the temporal fossa through a petrosquamous sinus (PSS) [5].
These aberrant vessels are usually asymptomatic but sometimes present with pulsatile tinnitus symptoms [6]. As it is commonly asymptomatic, it is usually an incidental finding on imaging. It was first radiologically described in 2001 by K. Marsot-Dupuch et al. This included the description of PSS from six patients using High-Resolution Computer Tomography (HRCT), complemented by Magnetic Resonance (MR) venography in three [1]. This emissary vein has also been studied using HRCT venography in a study on thirty patients with 39 temporal embryological variations [7].
We present this report as a template for the use of DSA techniques in a tertiary healthcare setup to help in improving outcomes in the case of otological surgeries that are complicated by the presence of aberrant vessels [1].
There are several clinical reasons to keep these vessels in mind. These emissary veins have been known to harbour the risk of extension of cortical venous thrombophlebitis to sigmoid sinuses in otological surgeries of the mastoid cavity, which may lead to cortical venous thrombosis [8].
This vein has an otological significance due to its close association with the auditory system, which can be seen as a possibility of retrograde spread of tumours or infection of the external auditory canal through PSS [1]The Petrosquamous sinus is also very important in deciding the approach for otological surgery; therefore, awareness of the aberrance should be given importance [9].
It has been hypothesised that in the cases of skull base anomalies [4] and jugular venous thrombosis [10], in which the emissary veins become an integral part of the venous drainage system, the blockage may lead to severe consequences for the patient. This furthermore increases the importance of investigations like the DSA, which will assess the significance of the emissary veins in the venous drainage system of the patient and identify a lesion, if present.
Our patient underwent a successful otological procedure and then showed excellent recovery post-surgery. She suffered no lasting effects of the pathology.
Author Contribution
All authors contributed equally to the paper.
Funding
The authors received no specific funding for this work.
Declarations
Conflict of interest
The authors have no conflicts of interest to declare.
Consent to Participate
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient and her guardian have given their written consent for her images and other clinical information to be reported in the journal. The patient understands that their names and initials will not be published, and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Ethical Approval
We have read and abided by the statement of ethical standards for manuscripts submitted to Indian Journal of Otolaryngology and Head and Neck Surgery.
Footnotes
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