Imaging of persistent bilateral occipital sinus with absent bilateral transverse sinus

Abstract

Persistent occipital sinus with absent/ hypoplastic bilateral transverse sinus is an extremely rare finding in adults; less than 10 cases have been reported. We present a case of a 28-year-old male who was brought to the emergency department in a post-ictal state associated with blurring of vision and 1 vomiting episode. Magnetic resonance imaging (MRI) with angiography and venography of the brain was advised, and the brain parenchyma was found to be anatomically normal. Incidental findings of the persistent occipital sinus with absent/ hypoplastic bilateral transverse sinus were made using venography imaging of the brain. This is a type of fetal presentation of venous blood flow. It is paramount to neurosurgeons because a prominent occipital sinus with an absent bilateral transverse sinus might change the surgical approach for the posterior fossa lesions.

Case report

A 28-year-old male patient, a shopkeeper by profession, was brought to the emergency department by his mother with complaints of teeth clenching for approximately 15 minutes, associated with 1 episode of vomiting and blurring of vision. The patient recalls no memory of the episode.

The patient was confused but oriented to time, place, and person. The respiratory rate was 16 breaths per minute and was normal. Blood pressure was 124/82 mm of mercury, and heart rate was 76 beats per minute.

The patient was a chronic alcoholic and had a history of drinking a minimum of 90ml of whisky daily for 12 years. His last drink was 1 day before the hospital visit. He has no significant medical history and is not a known case of systemic illness. The family history reveals nothing significant. There was no history of fever, head trauma, any known illness, or lack of sleep. There was no history of any medication or drug intake. He was lean-built, and there were no known risk factors for cerebral venous thrombosis other than the chief complaints provided.

A complete blood count, liver function test, kidney function test, and vitamin B12 test were performed, all within normal limits as shown in Table 1.

Table 1.

Tabulated results of the patient's investigations.

Investigation	Patient	Reference values
Hemoglobin	13.1	12.1-15.1 g/dL
MCHC	34.4	32-36 g/dL
MCV	88.2	80-100 fl
MCH	27.4	27-33 pg
Total RBC count	4.9	4.3–6.1 cells/mcl
Total WBC count	8200	4000-9000 g/dL
Total platelet count	240000	150,000-400,000 g/dL
HCT	39.1	36-44%
Granulocytes	6.8	1.5-8.5 ×10^9/L
RDW	13.8	12.2-16.1%
APTT	30	21-35 seconds
Prothrombin time	11.3	10-13 seconds
INR	0.9	<1.2
Urea	16	5-20 mg/dL
Creatinine	0.8	0.6-1.1 mg/dL
Vitamin B12	330	160-950 pg/mL

A provisional diagnosis of seizure was made, and a magnetic resonance imaging (MRI) with magnetic resonance angiography (MRA) and magnetic resonance venogram (MRV) of the brain was advised to rule out any organic cause.

MRI and MRA of the brain revealed the normal appearance of the brain parenchyma and its arterial supply. MRV revealed the absence of bilateral transverse sinus with persistent occipital sinus dividing into 2 and draining into the marginal sinus and the internal jugular veins. A sigmoid sinus was present bilaterally and drained into the internal jugular veins. A condylar vein was present, which was seen at the origin of the sigmoid sinus bilaterally, as shown in Fig. 1, Fig. 2, Fig. 3.

Fig. 1.

Time-of-flight magnetic resonance venography coronal view in a 27-year-old male showing persistent bilateral occipital sinus (orange arrows), draining into the bilateral jugular veins (green arrows) via bilateral marginal sinus (yellow arrows). There is an absence of a bilateral transverse sinus. Bilateral sigmoid sinus (blue arrows), superior sagittal sinus (gray arrow), and bilateral condylar vein are visualized (purple arrows).

Fig. 2.

Time-of-light magnetic resonance venography oblique coronal view in a 27-year-old male showing persistent bilateral occipital sinus (orange arrows), draining into the bilateral jugular veins (green arrows) via bilateral marginal sinus (yellow arrows). There is an absence of a bilateral transverse sinus. Bilateral sigmoid sinus (blue arrows), superior sagittal sinus (gray arrow), straight sinus (red arrow), and condylar vein are visualized (purple arrow).

Fig. 3.

Time-of-flight magnetic resonance venography oblique axial view in a 27-year-old male showing persistent occipital sinus (orange arrow), draining into the jugular veins (green arrows) via marginal sinus (yellow arrow). There is an absence of a bilateral transverse sinus. Sigmoid sinus (blue arrows), superior sagittal sinus (gray arrow), straight sinus (red arrow), and bilateral condylar vein are visualized (purple arrows).

A neurologist's call was made the next day when the patient was oriented to time, place, and person, and any organic cause for the above complaints was ruled out. The patient was given a detailed explanation of his low-risk category for the development of similar symptoms and was advised to take sodium valproate to reduce the chances of recurrence further.

The patient refused any treatment because of monetary issues and was discharged with advice to follow up after 2 months or if a similar episode recurs.

Discussion

Venous blood from the brain reaches systemic circulation by venous channels. Numerous smaller channels drain into the bigger venous sinuses, connected to the systemic circulation via internal jugular veins. Transverse sinus, occipital sinus, superior sagittal sinus, and straight sinus form the torcular herophili a/k/a confluence of sinuses [1].

The occipital sinus is prominent in the developing fetus and empties into the internal jugular veins through the marginal sinus. At the time of birth, the occipital sinus regresses, and the transverse sinus drains into the internal jugular veins through the sigmoid sinus, which forms the main venous drainage pathway. However, in very few people, the fetal presentation of the venous drainage system, i.e., occipital sinus draining into the marginal sinus and terminating into the internal jugular veins, persists [2,3].

We present a case of incidental finding of persistence of bilateral occipital sinus and regression of bilateral transverse sinus in a patient presenting to us in a post-ictal state.

This case report demonstrates the MRV appearance of the prominent bilateral occipital sinus draining into the bilateral marginal sinus and terminating into the bilateral jugular veins with a condylar vein at the origin of the sigmoid sinus bilaterally. This appearance is extremely rare; less than 10 such cases with imaging features have been reported in the literature.

Dural venous sinuses are a bunch of vascular channels or sinuses draining the circulating venous blood from the cranial cavity. They return the blood from the head into the systemic circulation. Meningeal and periosteal layers of the dura matter contain 7 major venous sinuses: cavernous sinus, superior sagittal sinus, straight sinus, inferior sagittal sinus, sigmoid sinus, transverse sinus, and superior petrosal sinus [[4], [5], [6]].

Embryologically, the occipital sinus is a minor venous channel most prominent in the fifth month of intrauterine life. They originate from the medial portions of the transverse sinus and the primitive torcula. With the advancement of the gestational age, occipital sinuses progressively reduce in caliber and number, and only a few individuals are born with the prominent occipital sinus. Normally, the occipital sinus lies in the midline, but it is not unusual to witness an occipital sinus not in the midline [2,3].

The occipital sinus tracks inferiorly from the torcula to the marginal veins and then empties into the jugular, suboccipital, or paravertebral venous plexus [2]. The occipital sinus receives some blood from the spine and spinal cord by communicating with the posterior internal vertebral plexus and is considered an emissary vein. The occipital sinus works as a substitute venous drainage pathway when the venous return via the internal jugular vein is affected. The occipital sinus becomes the dominant pathway for venous drainage in cases of absent transverse sinus [1].

There is no gender predilection associated with the prominence of the occipital sinus, and patients are mostly asymptomatic. Noncontrast computed tomography (NCCT) plays no role in the diagnosis. Contrast-enhanced computed tomography (CECT) might show a clear anatomical depiction and help identify the anomaly. MRV is the investigation of choice displaying complete anatomy and other associated venous anomalies [7].

Knowledge about the persistence of the occipital sinuses with absent transverse sinuses is crucial in various approaches for patients undergoing surgical interventions for the posterior fossa lesions, including the retro-sigmoid approach [8].

Patient consent

An informed verbal and written consent was obtained from the patient.