ISSN 0017-8748 doi: 10.1111/head.12437 Published by Wiley Periodicals, Inc.
Headache © 2014 American Headache Society
Clinical Correspondence Intrapontine Root Entry Zone FLAIR Hyperintensity in Classical Trigeminal Neuralgia Dimitri Renard, MD; Anne Le Floch, MD; Cecile Aerts, MD; Cornelia Freitag, MD; Fabricio Pereira, PhD Key words: trigeminal neuralgia, FLAIR, hyperintensity, root entry zone (Headache 2014;54:1543-1544)
We report a patient with trigeminal neuralgia associated with neurovascular conflict. Small size fluid attenuated inversion recovery (FLAIR) hyperintensity at the intrapontine trigeminal root entry zone (REZ) was seen, in the absence of arguments in favor of an ischemic or primary demyelinating process. The suspected cause of the hyperintensity was a process, a demyelination secondary to vascular compression.We propose to analyze larger numbers of patients with classical trigeminal neuralgia to look for these small, easily overlooked, REZ hyperintensities. A 53-year-old woman presented, without cardiovascular risk factors, and an 8-year history (with progressive symptom onset on the age of 45) of rightsided trigeminal neuralgia (TNA). Clinical examination showed no (ie, neither at symptom onset nor during follow-up) sensory trigeminal disturbances. One year after symptom onset (age 46 years), magnetic resonance imaging (MRI) showed a small 1.3 × 3 mm zone of antero-lateral FLAIR From the Department of Neurology, CHU Nîmes, Hôpital Caremeau, Nîmes, France (D. Renard, A. Le Floch, and C. Aerts); Medical Imaging Group (MIG) Nîmes, Department of Radiology, CHU Nîmes, Hôpital Caremeau, Nîmes, France (C. Freitag and F. Pereira). Address all correspondence to D. Renard, Place du Pr Debré, 30029 Nîmes Cedex 4, France. Accepted for publication June 28, 2014.
hyperintensity at the right-sided intrapontine trigeminal REZ without other brain abnormalities except for a suspected neurovascular conflict between the trigeminal nerve (TN) and the superior cerebellar artery branches. Surgery, 1 year later, confirmed that the neurovascular conflict and microvascular decompression led to partial pain relief. FLAIR hyperintensity was stable on MRI at age 53 years and no other signal abnormalities appeared (Figure). Diffusion-tensor imaging showed decreased fractional anisotropy (FA) in the right-sided intrapontine REZ and TN (ie, FA values 30% lower than on the left side) without clear changes in mean diffusivity (Figure). Informed consent was given by the patient. The most frequent cause of TNA is a mechanical irritation of the TN originating from neurovascular compression at the nerve’s REZ. Intrapontine lesions (eg, infarction, multiple sclerosis-related demyelinating lesions) involving central trigeminal pathways have been reported in some cases of TNA. In patients with intrapontine lesions, sensory trigeminal disturbances are more frequent. In multiple sclerosis, linearly shaped intrapontine lesions are sometimes described. The absence of clinical and radiological evolution after 8 years of follow-up made a diagnosis of multiple sclerosis unlikely in our patient. In case of infarction, symptom onset is often acute and lesions
Conflict of Interest: None.
1543
1544
October 2014
Figure.—1.5T brain magnetic resonance imaging showing a small area (1.3 × 3 mm) of FLAIR hyperintensity in the right-sided intrapontine root entry zone (REZ) (A and B, arrows). Diffusion-tensor imaging (C) demonstrating reduced fractional anisotropy (FA) in the right-sided REZ (arrow) on the color-coded FA map (arrowhead is showing the left-sided REZ).
tend to be larger than in our patient. Although an isolated small size infarction could not be excluded in our patient, this hypothesis is unlikely given her relatively young age at symptom onset, the absence of cardiovascular risk factors, and the lack of other ischemic lesions on MRI. All reported patients with TNA associated with pontine infarction were older than our patient at symptom onset and had larger (and often linear or wedge-shaped as opposed to our case) signal abnormalities on MRI. FA reflects the degree of directionality in brain microstructures. Decreased FA has been earlier described in both the TN and the REZ suggesting the presence of less fiber organization and/or atrophy in these structures.1-3 In some of these studies, associated increased mean, radial, and/or axial diffusity has been observed, suggesting a process of demyelination, inflammation, or edema. Demyelination of trigeminal fibers has been histopathologically proven in patients with so-called idiopathic TNA.4 The suspected cause of the small intrapontine REZ FLAIR hyperintensity in our patient was a process a demyelination secondary to vascular compression. To the best of our
knowledge, this very small REZ FLAIR hyperintensity (thought to be secondary to vascular compression) has never been described in classical TNA. We propose to analyze larger numbers of patients with classical TNA to look systematically for these small, easily overlooked, REZ FLAIR hyperintensities.
REFERENCES 1. Liu Y, Li J, Butzkueven H, et al. Microstructural abnormalities in the trigeminal nerves of patients with trigeminal neuralgia revealed by multiple diffusion metrics. Eur J Radiol. 2013;82:783-786. 2. Desouza DD, Hodaie M, Davis KD. Abnormal trigeminal nerve microstructure and brain white matter in idiopathic trigeminal neuralgia. Pain. 2014;155:3744. 3. Herweh C, Kress B, Rasche D, et al. Loss of anisotropy in trigeminal neuralgia revealed by diffusion tensor imaging. Neurology. 2007;68:776-778. 4. Love S, Hilton DA, Coakham HB. Central demyelination of the Vth nerve root in trigeminal neuralgia associated with vascular compression. Brain Pathol. 1998;8:1-11.
Headache © 2014 American Headache Society
Clinical Correspondence Intrapontine Root Entry Zone FLAIR Hyperintensity in Classical Trigeminal Neuralgia Dimitri Renard, MD; Anne Le Floch, MD; Cecile Aerts, MD; Cornelia Freitag, MD; Fabricio Pereira, PhD Key words: trigeminal neuralgia, FLAIR, hyperintensity, root entry zone (Headache 2014;54:1543-1544)
We report a patient with trigeminal neuralgia associated with neurovascular conflict. Small size fluid attenuated inversion recovery (FLAIR) hyperintensity at the intrapontine trigeminal root entry zone (REZ) was seen, in the absence of arguments in favor of an ischemic or primary demyelinating process. The suspected cause of the hyperintensity was a process, a demyelination secondary to vascular compression.We propose to analyze larger numbers of patients with classical trigeminal neuralgia to look for these small, easily overlooked, REZ hyperintensities. A 53-year-old woman presented, without cardiovascular risk factors, and an 8-year history (with progressive symptom onset on the age of 45) of rightsided trigeminal neuralgia (TNA). Clinical examination showed no (ie, neither at symptom onset nor during follow-up) sensory trigeminal disturbances. One year after symptom onset (age 46 years), magnetic resonance imaging (MRI) showed a small 1.3 × 3 mm zone of antero-lateral FLAIR From the Department of Neurology, CHU Nîmes, Hôpital Caremeau, Nîmes, France (D. Renard, A. Le Floch, and C. Aerts); Medical Imaging Group (MIG) Nîmes, Department of Radiology, CHU Nîmes, Hôpital Caremeau, Nîmes, France (C. Freitag and F. Pereira). Address all correspondence to D. Renard, Place du Pr Debré, 30029 Nîmes Cedex 4, France. Accepted for publication June 28, 2014.
hyperintensity at the right-sided intrapontine trigeminal REZ without other brain abnormalities except for a suspected neurovascular conflict between the trigeminal nerve (TN) and the superior cerebellar artery branches. Surgery, 1 year later, confirmed that the neurovascular conflict and microvascular decompression led to partial pain relief. FLAIR hyperintensity was stable on MRI at age 53 years and no other signal abnormalities appeared (Figure). Diffusion-tensor imaging showed decreased fractional anisotropy (FA) in the right-sided intrapontine REZ and TN (ie, FA values 30% lower than on the left side) without clear changes in mean diffusivity (Figure). Informed consent was given by the patient. The most frequent cause of TNA is a mechanical irritation of the TN originating from neurovascular compression at the nerve’s REZ. Intrapontine lesions (eg, infarction, multiple sclerosis-related demyelinating lesions) involving central trigeminal pathways have been reported in some cases of TNA. In patients with intrapontine lesions, sensory trigeminal disturbances are more frequent. In multiple sclerosis, linearly shaped intrapontine lesions are sometimes described. The absence of clinical and radiological evolution after 8 years of follow-up made a diagnosis of multiple sclerosis unlikely in our patient. In case of infarction, symptom onset is often acute and lesions
Conflict of Interest: None.
1543
1544
October 2014
Figure.—1.5T brain magnetic resonance imaging showing a small area (1.3 × 3 mm) of FLAIR hyperintensity in the right-sided intrapontine root entry zone (REZ) (A and B, arrows). Diffusion-tensor imaging (C) demonstrating reduced fractional anisotropy (FA) in the right-sided REZ (arrow) on the color-coded FA map (arrowhead is showing the left-sided REZ).
tend to be larger than in our patient. Although an isolated small size infarction could not be excluded in our patient, this hypothesis is unlikely given her relatively young age at symptom onset, the absence of cardiovascular risk factors, and the lack of other ischemic lesions on MRI. All reported patients with TNA associated with pontine infarction were older than our patient at symptom onset and had larger (and often linear or wedge-shaped as opposed to our case) signal abnormalities on MRI. FA reflects the degree of directionality in brain microstructures. Decreased FA has been earlier described in both the TN and the REZ suggesting the presence of less fiber organization and/or atrophy in these structures.1-3 In some of these studies, associated increased mean, radial, and/or axial diffusity has been observed, suggesting a process of demyelination, inflammation, or edema. Demyelination of trigeminal fibers has been histopathologically proven in patients with so-called idiopathic TNA.4 The suspected cause of the small intrapontine REZ FLAIR hyperintensity in our patient was a process a demyelination secondary to vascular compression. To the best of our
knowledge, this very small REZ FLAIR hyperintensity (thought to be secondary to vascular compression) has never been described in classical TNA. We propose to analyze larger numbers of patients with classical TNA to look systematically for these small, easily overlooked, REZ FLAIR hyperintensities.
REFERENCES 1. Liu Y, Li J, Butzkueven H, et al. Microstructural abnormalities in the trigeminal nerves of patients with trigeminal neuralgia revealed by multiple diffusion metrics. Eur J Radiol. 2013;82:783-786. 2. Desouza DD, Hodaie M, Davis KD. Abnormal trigeminal nerve microstructure and brain white matter in idiopathic trigeminal neuralgia. Pain. 2014;155:3744. 3. Herweh C, Kress B, Rasche D, et al. Loss of anisotropy in trigeminal neuralgia revealed by diffusion tensor imaging. Neurology. 2007;68:776-778. 4. Love S, Hilton DA, Coakham HB. Central demyelination of the Vth nerve root in trigeminal neuralgia associated with vascular compression. Brain Pathol. 1998;8:1-11.
