Cranial nerves MRI: When things are not so straight forward
Poster No.:
C-2540
Congress:
ECR 2010
Type:
Educational Exhibit
Topic:
Neuro
Authors:
C. González, M. Fernández del Castillo, E. Alventosa, A. Bello, V.
Martín; Santa Cruz de Tenerife/ES
Keywords:
Cranial nerves, Magentic Resonance Imaging, Head and neck
DOI:
10.1594/ecr2010/C-2540
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Page 1 of 12
Learning objectives
To illustrate cranial nerves imaging besides the main character in this setting, vestibular
schwanoma, and to offer some tips in cranial nerves MRI.
Vestibular schwannoma account for 95% of intracranial schwannoma followed by
trigeminal and facial and then glossopharyngeal, vagus and spinal accessory nerve
schwannomas. Acoustic schwannomas are located within the internal auditory canal,
either being completely intracanalicular or extending into the cerebellopontine angle
(typically with an "ice cream" configuration-figure 1b on page 2-). Virtually 100% of
patients with bilateral acoustic schwannomas will have neurofibromatosis. Schwannomas
are focal and encapsulated and they are often cystic with hemorrhage and necrosis
common. Keys to the diagnosis are the neuroanatomic location of the tumor, its extension
following the courses of the nerves, smooth enlargement of their foramina,
and fatty amyotrophy of the corresponding enervated muscles.
In this section we show various cranial nerves schwannomas including many faces of
acoustic schwannoma (figure 1 on page 2), X (figure 2 on page 4) and VII (figure
3 on page 4)schwannomas offering some tips in diagnosis of thecommonest cranial
nerves primary tumor.
Images for this section:
Page 2 of 12
Page 3 of 12
Fig. 1: Figure 1: Many faces of Acoustic Schwannoma: 1a) Axial T1 + Gd: Intracanalicular
acoustic schwannoma as focal enhancing mass in the left internal auditory canal.
Incidentally a meningioma close to the left cerebellopontine angle was encountered.
1b) Axial T1 +Gd: Acoustic schwannoma extending into the cerebellopontine angle with
the typical "ice cream configuration". 1c) Axial SSFP: Large vestibular schwannoma
with cystic changes enlarging the left cerebellopontine cistern causing compression and
contralateral deviation of the pons.
Fig. 2: Figure 2: X Cranial Nerve Schwannoma: Well defined homogenous fusiform
right laterocervical mass (a- PD coronal MRI) with CT images correlation (b and c:
coronal reconstruction and axial image). Some tips to the diagnosis of cranial nerves
schwannomas are the neuroanatomic location ant its extension following the courses
of the nerves. In the neck, the vagus nerve lies within the carotid sheath, behind and
between the internal jugular vein and common carotid artery.
Fig. 3: Figure 3: VII Cranial Nerve Schwannoma: Encapsulated round intraparotid mass
on the left side extending through the petrous portion of the VII cranial nerve. Note
enlargement of the stylomastoid foramen supporting facial nerve origin.
Page 4 of 12
Background
There is a variety of disorders which can cause cranial nerves symptoms including
neoplastic, inflammatory and vascular conditions. MRI is invaluable in characterizing
disease of the cranial nerves. Steady-state free precession (SSFP) sequences are
particularly useful for visualizing the cisternal segments of cranial nerves because they
provide excellent contrast resolution between CSF and nerves.
Anatomy of cranial nerves is complex and is mandatory an in depth understanding of
the normal aspect of these structures. Conventional MR imaging may lack the spatial
resolution necessary to throroughly study cranial nerves. Several sequences have been
suggested in order to improve cranial nerves imaging. PROPELLER multishot diffusionweighted has been studied for depiction of cranial nerves within the brain stem but
improvements are needed to apply it on a clinical basis. Steady state free precession
(SSFP) sequences definitively allow much higher spatial resolution and clearer depiction
of cranial nerves than conventional MR imaging. SSFP are particularly useful for
visualizing the cisternal segments of cranial nerves because they provide excellent
contrast resolution between CSF and nerves. Nevertheless, SSFP sequences play a
suplemental role alongside traditional MRI sequences.
In this section you can recognize some cranial nerves anatomy (V (a), III (b), VI and VII
(c)) on SSFP sequence (figure 4 on page 5).
Images for this section:
Page 5 of 12
Fig. 1: Figure 4: V, III, VII and VIII cranial nerves anatomy with an SSFP sequence. 4.a)
Trigeminal nerve (V): SSFP MR image shows the trigeminal nerve roots where they cross
the prepontine cistern and enter Meckel cave. 4.b) Oculomotor nerve (III) lying medial
to the cerebellar peduncle after leaving the interpeduncular cistern. 4.c) Facial (VII) and
vestibular (VIII) nerves in the internal auditory canal after crossing the cerebellopontine
angle.
Page 6 of 12
Imaging findings OR Procedure details
We show the imaging findings in a variety of conditions causing cranial nerves symptoms
divided into vascular (Fig. 1 on page 7; Fig. 2 on page 7), inflammatory (Fig.3 on
page 8; Fig. 4 on page 9) and neoplastic (Fig. 5 on page 10; Fig. 6 on page
10; Fig. 7 on page 10) origin emphasizing the importance of fully understanding
the unique normal and pathologic features of each cranial nerve.
Images for this section:
Fig. 1: Axial CT and MR: Bilateral intracavernous carotid elongation demonstrated in a
patient addressed for clinical suspicious of Tolossa-Hunt Syndrome.
Page 7 of 12
Fig. 2: Patient with left abducens nerve paresis whom imaging study (axial SSFP MRI)
demonstrated vascular compression of the VI cranial nerve (blue arrow) by a thrombosed
saccular aneurysm of the basilar artery (white arrow). Red arrow points the anteroinferior
cerebellar artery, another important vascular landmark for this cranial nerve.
Page 8 of 12
Fig. 3: Axial FLAIR (a) and coronal T2-FSE (b) images of a patient with multiple sclerosis
presenting with left trigeminal symptoms that revealed a demyelinating plaque at the
ipsilateral V nucleus on the midpons.
Fig. 4: Axial T1 (a) and axial PD FS (b) MRI. Malignant external otitis in a diabetic patient
with extensive inflammatory changes in the petrous bone involving right lower cranial
nerves.
Page 9 of 12
Fig. 5: Axial T1 (a), T1 FS (b) and SSFP (c) of a patient with left trigeminal neuralgia,
showing a well defined fatty mass involving the cisternal segment of V cranial nerve and
Meckel cave. This lesion is consistent with a lipoma.
Fig. 6: Axial T1 (a), T1 post-Gd (b) and magnetic susceptibility sequences showing a well
defined enhancing mass at the right cerebellar pontine angle extending to the ipsilateral
cavernous sinus. Note the dural tail sign and multiple signal loss on c image due to a
partially calcified meningioma.
Page 10 of 12
Fig. 7: Axial T1 pre (a) and post-Gd (b) showing enlargement and enhacement of left V
cranial nerve and Meckel cave in a patient with a known head and neck malignancy. This
is an example of perineural spread tumor.
Page 11 of 12
Conclusion
We show the imaging findings in a variety of conditions causing cranial nerves symptoms
including abnormal enhancement, benign primary tumors, perineural cranial nerve tumor
spread and rare neoplasm involving cranial nerves, demyelinating disease, compression
by osseous, vascular and inflammatory disorders, emphasizing the importance of fully
understanding the unique normal and pathologic features of each cranial nerve.
Personal Information
References
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