Delayed gadolinium contrast-enhanced 3D-T1 SPACE STIR sequence can better visualize abnormal cranial nerves: a case report

Abstract

With the advancement of magnetic resonance imaging (MRI) techniques, general radiographic methods are no longer sufficient for accurately displaying the structure and pathway of cranial nerves. Various sequences, including 3-dimensional sampling perfection with application-optimized contrast using different flip angle evolution (SPACE), have been developed through MRI technology to effectively display the location and severity of damaged cranial nerves. This current case report describes a 36-year-old male patient with multiple cranial nerve injuries resulting from an invasive Mucor infection. While performing MRI scanning on this patient, a 1-h delayed enhanced MRI 3D-T1 SPACE short tau inversion recovery (STIR) sequence proved more effective in eliminating background interference and assessing neurological damage with greater clarity than conventional enhancement methods. This approach may prove beneficial in accurately evaluating the extent of cranial neuropathy, thus facilitating clinical applications.

Introduction

The slender anatomy, complex pathways and overlapping surrounding structures make it challenging to obtain clear visualizations of the cranial nerve using ordinary radiographic imaging methods. As a result, the diagnosis of the underlying causes of cranial nerve-related diseases can prove challenging. A challenge for general radiology is displaying the cranial nerve and its surrounding anatomical structures. With the rapid development of magnetic resonance imaging (MRI) technology, steady-state free precession MRI, Cassini Imaging Science Subsystem (CISS), fast imaging employing steady-state acquisition (FIESTA), sampling perfection with application-optimized contrast using different flip angle evolution (SPACE), volume isotropic turbo spin echo acquisition (VISTA) and 3-dimensional-fluid attenuated inversion recovery (3D-FLAIR), are being utilized for diagnosing pathologies related to the cranial nerves.^1,2 Currently, 3D SPACE sequence imaging is extensively used in clinical practice for diagnosing cranial nerve pathologies, particularly in the cisternal segment, owing to its optimal imaging efficacy and shorter scanning duration. Recent studies have found that the T1-enhanced 3D SPACE short tau inversion recovery (STIR) sequence achieved satisfactory results in imaging the brachial plexus, lumbosacral plexus and partial cranial nerves.^3,4 However, the effectiveness of displaying injured cranial nerves is influenced by the degree of enhancement, including scanning delay time, contrast material dosage and individual factors. Therefore, clinicians need to possess ample experience in precisely evaluating the extent of cranial neuropathy and recognizing the correlation between neuropathy and nerves. Previous research has demonstrated that obtaining an MRI with a delayed FLAIR sequence (1 h) following intravenous injection is a rapid and effective technique for diagnosing acute superior vestibular neuritis. ⁵

Despite the progress made, there currently needs to be more research on the efficacy of delayed contrast-enhanced scanning for other cranial nerve injuries. This current case report describes a patient with multiple cranial nerve injuries resulting from an invasive Mucor infection. During the investigation to identify the site and severity of the cranial nerve injuries, a1-h delayed enhanced MRI 3D-T1 SPACE STIR sequence was found to effectively reduce background interference and provide a more precise assessment of the neurological damage. The findings from this current case suggest that determining the appropriate timing for MRI examinations of injured cranial nerves is beneficial in clinical settings.

Case report

In July 2021, a 36-year-old male patient was admitted to the Department of Neurology, Harrison International Peace Hospital, Hengshui, Hebei Province, China as a result of 1.5 days of mouth askew, which was accompanied by a day of headache and fever. The patient had been admitted 1 month previously to the Department of Endocrinology at the same hospital due to diabetic ketoacidosis. Upon admission, a physical examination of the nervous system showed that the patient was conscious, although his speech was less fluent. He had right peripheral facial paralysis, a right deviation of the protruding tongue, normal muscle strength and limb tension, and a negative Babinski sign on both sides. After admission, limited movement gradually developed in the patient’s right eye. On the fourth day of admission, a physical examination of his nervous system revealed consciousness, a hoarse voice, right eyelid ptosis and a fixed right eyeball without exophthalmos. The patient’s right frontal striae disappeared, the right nasolabial fold became shallow and his tongue protruded toward the right. Moreover, the pain sensation on the right side of the face had decreased. The muscle strength and tension of the limbs appeared normal. However, the meningeal irritation sign was positive. Upon conducting a lumbar puncture examination, it was observed that the pressure was 150 mmH₂O, with yellowish colour and a white blood cell count of 654 × 10⁶/l (normal range, 0–8 × 10⁶/l). The protein level was 1.23 g/l (normal range, 0.15–0.45 g/l), the chloride level was 109 mmol/l and the glucose level was 2.45 mmol/l. Additionally, cytology revealed a hybrid cytological reaction; and the metagenomic next-generation sequencing Rhizopus oryzae sequence number was 148. The total length covered on the genome was 10927 base pairs, the coverage was 0.027036% and the median depth was 1.00 X. Conventional plain computed tomography and MRI scans were normal. MRI undertaken with 3D-T1 SPACE STIR sequence revealed abnormal enhancement around the facial nerve, trigeminal nerve, posterior orbital wall, right maxillary sinus and oral maxillofacial spaces. MRI re-examination for the disease changes after 2 h showed that the enhancement of the facial nerve, trigeminal nerve (Figure 1) and posterior orbital wall (Figure 2) was persistent and became more apparent. As R. oryzae is classified under the Mucor genus, the patient was clinically diagnosed with Rhino-orbital-cerebral mycosis and promptly treated with amphotericin B (50 mg amphotericin B via intravenous drip once a day for 3 weeks in the hospital). After 3 weeks of hospitalization, the patient was discharged due to economic difficulties and received antifungal therapy at home (50 mg amphotericin B via intravenous drip once a day for 5 weeks at home).

Figure 1.

Enhanced magnetic resonance imaging (MRI) with T1-enhanced 3-dimensional sampling perfection with application-optimized contrast using different flip angle evolution short tau inversion recovery (3D-T1 SPACE STIR) sequence results of a 36-year-old male patient admitted as a result of 1.5 days of mouth askew accompanied by a day of headache and fever (a standard dose of gadolinium). The MRI 3D-T1 SPACE STIR showed slightly enhanced facial nerve (a & c) and trigeminal nerve (e & g) (red arrow). Re-examination of MRI 3D-T1 SPACE STIR with a 1-h delay more clearly revealed enhanced facial nerve (b & d) and trigeminal nerve (f & h) (red arrow). The colour version of this figure is available at: http://imr.sagepub.com.

Figure 2.

Conventional enhanced magnetic resonance imaging (MRI) of a 36-year-old male patient admitted as a result of 1.5 days of mouth askew accompanied by a day of headache and fever was not able to identify the enhancement of the back wall of the eyeball accurately due to background interference (red arrow) (a). Delayed enhanced MRI showed the enhancement clearly (red arrow) (b). The colour version of this figure is available at: http://imr.sagepub.com.

This study obtained ethical approval from the institutional review board of Harrison International Peace Hospital, Hengshui, Hebei Province, China (no. 2019-1-024). The patient provided written informed consent after being fully informed about the treatment and before treatment commenced. The reporting of this study conforms to CARE guidelines. ⁶

Discussion

The cranial nerve travels to various parts of the head and neck through the bony foramina and meninges of the skull base, making it vulnerable to local or systemic lesions. Malignant tumours, infections, vasculitis and immune and connective tissue diseases disorders are among the diseases that can simultaneously affect multiple cranial nerves. General radiographic techniques need to be improved to display the structure and pathway of the cranial nerve. The development of MRI technology has made it possible to visualize the location and severity of damaged cranial nerves. To show the intracranial segment of the cranial nerve, some sequences such as 3D-CISS and 3D-FIESTA are used, which reveal the natural contrast with cerebrospinal fluid on the T2W sequence as the intracranial segment of the cranial nerve runs through the cerebrospinal fluid of the subarachnoid space, making them more reliable methods than a T2 plain scan.^7,8 However, the above methods have limited application for the peripheral segment of the cranial nerve as it exits the skull through the foramens of the skull base. Some studies have displayed the peripheral segment of the cranial nerve using the 3D-dual echo steady state-water excitation sequence, the fast imaging with steady-state precession sequence and the 3D-FIESTA sequence combined with the fat suppression technique.^{3, 9} However, there are still challenges in displaying small branches. While the T1 enhanced 3D-T1 SPACE STIR sequence has demonstrated relatively satisfactory results in imaging the brachial plexus, lumbosacral plexus, and some cranial nerves, it still needs to be combined with other conventional MR sequences for identifying and evaluating structures such as muscles, blood vessels, fat spaces and glands. ¹⁰ There are also various issues, such as background interference.

The current patient was first admitted to hospital with a cranial nerve injury. As his condition worsened, multiple cranial nerve damage (including glossopharyngeal, vagus, hypoglossal, trigeminal nerve, facial nerve, oculomotor nerve, trochlear nerve and abducens nerve) and meningitis-like features appeared successively. Comprehensive patient analysis and identification of the cranial nerve injury sites were necessary for accurate diagnosis and treatment. The 3D-T1 SPACE STIR sequence enhancement revealed eccentric strengthening of the right lateral nerve and trigeminal nerve, clearly displaying the injured site of the cranial nerve. However, the diagnosis still required careful identification by experienced physicians due to background interference, which made it difficult to determine. The patient underwent a re-examination using an enhanced 3D-T1 SPACE STIR sequence due to changes in his condition 2 h after the first examination. The result showed that the right facial nerve and trigeminal nerve were more clearly displayed, with significantly reduced background interference. There are no reports on using delayed enhancement in the 3D-T1 SPACE STIR sequence for cranial nerve examination. However, previous studies have shown that in the enhanced scan of the gadolinium-diethylenetriamine penta-acetic acid (Gd-DTPA) using the 3D-T1 SPACE STIR sequence, a low concentration of Gd-DTPA has a more significant influence on the T1 relaxation time of body tissue.¹¹ In contrast, the effect of shortening T2 relaxation time becomes more pronounced with increasing Gd-DTPA concentration. ¹¹ Although a standard dose of Gd-DTPA (manufactured by Jiangsu Hengrui Medicine, Lianyungang, Jiangsu Province, China) was applied to the current patient, delayed scanning was employed to minimize the dose of Gd-DTPA in the body. This resulted in the tissues that absorb the contrast medium, such as muscles, vascular plexus, bone marrow and salivary glands, displaying a low signal on the 3D-T1 SPACE STIR sequence, thus highlighting the high signal of the peripheral neural fasciculus rich in bound water. Regarding the mechanism of continuous enhancement of the cranial nerve, it is hypothesized that the invasion of Mucor leads to the destruction of the blood–nerve barrier and demyelination, allowing the macromolecule Gd-DTPA to enter the cranial nerve and diffuse along the perineurium clearance. The paramagnetic contrast agent then increases the signal of the corresponding nerve segment by altering the T1 relaxation time. However, this specific mechanism requires further investigation. In addition, the patient’s right eyeball appeared to be fixed without exophthalmos, and no evidence of enhancement of the oculomotor, trochlear and abducens nerve was observed. It was suggested that the patient may be experiencing incomplete orbital apex syndrome or supraorbital fissure syndrome, which could be attributed to the enhancement of the posterior wall of the eyeball. Conventional enhancement techniques failed to identify the enhanced area accurately due to background interference. However, the delayed enhancement could display the enhancement of the posterior wall of the eyeball clearly.

Compared with conventional neuroimaging sequences such as enhanced 3D SPACE STIR and plain scan 3D SPACE STIR, delayed enhancement 3D-T1 SPACE STIR sequence provides higher contrast images with a remarkable background suppression effect. This could facilitate an accurate assessment of the degree of cranial neuropathy accurately and make it more suitable for clinical applications. However, the delay time still needs to be clarified, and there is a lack of comparative studies with large sample sizes, so further research is still needed.

Supplemental Material

sj-pdf-1-imr-10.1177_03000605231179817 - Supplemental material for Delayed gadolinium contrast-enhanced 3D-T1 SPACE STIR sequence can better visualize abnormal cranial nerves: a case report

Supplemental material, sj-pdf-1-imr-10.1177_03000605231179817 for Delayed gadolinium contrast-enhanced 3D-T1 SPACE STIR sequence can better visualize abnormal cranial nerves: a case report by Lu Zhang, Zhilei Kang, Mingyue Hu and Jingzhe Han in Journal of International Medical Research