Download The Medial Longitudinal Fasciculus in Multiple Sclerosis

The Medial Longitudinal Fasciculus in Multiple Sclerosis
Poster No.:
C-2479
Congress:
ECR 2012
Type:
Educational Exhibit
Authors:
J. Ryan , A. Cahalane , E. Staneley ; IE, Dublin, Dublin/IE,
1
2
3 1
2
3
Dublin/IE
Keywords:
Inflammation, Imaging sequences, MR, Neuroradiology brain
DOI:
10.1594/ecr2012/C-2479
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Learning objectives
1) To review the conventional MRI findings that occur as a result of multiple sclerosis
(MS).
2) To evaluate the MRI imaging which results in the ocular clinical manifestation of
internuclear ophthalmoplegia (INO).
Background
Multiple sclerosis (MS) is an autoimmune inflammatory CNS demyelinating disease
1
which affects 2-150 people per 100,000 , with the highest incidence among women of
Northern European descent who are of child-bearing age.
The exact pathological mechanism of MS is unclear however the most widely accepted
2
theory is that it occurs as a result of autoreactive lymphocytes , which occurs as a result
of infective, environmental or genetic factors trigger factors.
There are no specific clinical features which are unique to MS, but so there are symtpoms
which are of the disease:
Presenting Symptom
% Occurrence
Sensory change in limbs
30.7
Visual Disturbannce
15.9
Motor Disturbance (Subacute)
8.9
Diplopia
6.8
Gait disturbance
4.8
Motor Disturbance (Acute)
4.3
Balance Abnormality
2.9
Lhermittes Sign
2.8
Verigo
Ref 3,4
1.8
MR sequences such as dual-echo, fluid-attenuated inversion-recovery (FLAIR), and
T1-weighted imaging, both pre- and post gadolinium-based contrast (Gd) provide key
information in diagnosing MS, as well as assessment of treatment.
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Dual echo and FLAIR sequence have the highest sensitivity in detection of MS plaques
where there is characteristically an increase in signal identified.
Optic neuritis is the most common ophthalmic manifestation of MS, with patients
5
presenting with unilateral eye pain worsened by movement , and subsequent clinical
examination may reveal a central scotoma and a Marcus Gunn pupil (afferent pupillary
defect).
The medial longitudingal fasiculus (MLF) are pair of white matter fiber tracts that
lie centrally beneath the fourth ventricle and cerebral aqueduct, and extend through
the dorsomedial pontine and midbrain tegmentum. They play an important roll in the
conjugate gaze as they provide a pathway for contralateral coordination between cranial
nerves III, IV, and VI and their interneuronal pathways.
Fig 1:
Internuclear ophthalmoplegia (INO) is a gaze abnormality characterized by impaired
horizontal eye movement, with weak adduction of the affected eye, and abduction
nystagmus of the contralateral eye.
Approximately one third of cases of INO occur as a result of MS involvment of the MLF
within the dorsomedial brainstem tegmentum.
The purpose of this educational exhibit is to review the conventional MRI findings in INO
in patients with a diagnosis of MS.
Images for this section:
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Fig. 1: Demonstration of Left Sided Nystagmus
Page 4 of 16
Imaging findings OR Procedure details
The diagnosis of MS is made on clinical examination with the initial Poser clinical criteria,
developed in the 1980s, being superseded by the McDonald criteria in 2001 which has
been twice updated (most recently in 2010) to incorporate new evidence and to simplify
6
the use of neuroimaging .
Conventional MR in Diagnosis MS:
The central requirement to a diagnosis of MS according to the McDonald criteria is the
demonstration of dissemination of CNS plaques in both time and space, either clinically
or in combination with MRI after clinical examination.
Dual-echo and FLAIR MRI imaging have a high sensitivity for detection of MS lesions
with T1 post gadolinium imaging allowing active lesion lesions to be distinguished from
inactive lesions.
Dissemination in space is demonstrated on MRI by one or more T2 lesions in at least
two of four MS-typical regions of the CNS (periventricular, juxtacortical, infratentorial, or
spinal cord) or by the development of a further clinical attack implicating a different central
nervous system site.
Dissemination in time can be shown by the presence of a new T2 gadolinium-enhancing
lesion on follow-up MRI, irrespective of its timing with reference to a baseline scan, or by
the development of a second clinical attack.
Plaques are the characteristic lesion of MS and are histologically composed of
7
perivascular T-lymphocytes with macrophages and plasma cell . Although the diagnosis
of MS is clinical, the sensitivity of MRI (>85%) surpasses that of all other non-invasive
clinical tests
8
.
Typical plaque locations are the:
•
•
•
Periventricular white matter (>80%).
Corpus callosum (50-85%)
Posterior fossa (10%)
The plaques can be characterised at MRI by their location, signal intensity and degree
of enhancement post gadolinium.
Fig 2:
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Fig 3:
Post contrast T1 enhancement reflects disruption in the blood brain barrier and
active inflammation. New MS plaques uniformly enhance while established plaques
demonstrate a peripheral rim enhancement pattern.
Fig 4:
Spinal Cord Involvement:
Fig 5:
MS plaques are found in the spinal cord in isolation in 10-20% of MS patients and the
dorsolateral cervical spine is most commonly affected.
These lesions appear as well circumscribed lesions within the cord on T2 and STIR
sequences, and may cross the grey-white matter interface.
Optic Neuritis:
9
Optic neuritis is the most common ocular presentation of MS and clinically maybe
unilateral or bilateral at presentation. Clinically optic neuritis manifests as ocular pain
exacerbated by movement, which may progressed to central vision loss.
Post contrast T1 MRI demonstrates inflammation of the optic nerve in 95% of patients
with optic neuritis
of systoms.
10
with enhancement remaining for an average of 30 after the onset
Fig 6:
Internuclear Opthalmoplegia:
INO describes abnormal horizontal ocular movements with lost or delayed adduction and
horizontal nystagmus of the abducting eye and occurs as a result of a lesion within the
MLF.
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Any traumatic, inflammatory or vasculitis process which affects the MLF may result in
this condition however the most common causes are cerebrovascular disease and MS,
9
with a prevalence of 17-41% within the MS patient population .
The MLF is the interneuronal pathway between ipsilateral abducens nerves (CN VI) and
contralateral oculomotor nerves (CN III), and so allows for coordinated horizontal gaze.
Fig 7:
The periventricular region of the MLF appears to be most commonly affected by
demyelination in patients with MS and plaques characteristically demonstrate increased
signal on FLAIR and post contrast imaging.
Fig 8:
Fig 9:
Proton density imaging should also be considered to rule out a lesion within the MLF as
this has a higher specificity than conventional MS sequences in ruling out lesions within
the brainstem tegmentum
12
.
Images for this section:
Fig. 2: Sagittal FLAIR: MS plaques perpendicular to the corpus callosum.
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Fig. 3: Axial T1 - MS plaques demonstrate a low signal as a result of axonal breakdown.
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Fig. 4: Post Gd T1: Rim enhancement post contrast indicating active inflammation.
Page 9 of 16
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Fig. 5: T2 MR: MS plaque within the cervical spine.
Fig. 6: Post Gd T1: Optic nerve enhancement consistent with optic neuritis.
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Fig. 7: Schematic Representation of Conjugate Gaze Co-ordination
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Fig. 8: Axial FLAIR - Increased signal in region of the MLF in the dorsal right pons.
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Fig. 9: Post Gd T1 - Increased signal within the region of the MLF in the dorsal right pons.
Page 14 of 16
Conclusion
Multiple sclerosis is an inflammatory, demyelinating disease of the central nervous
system. MS lesions, characterized by perivascular infiltration of monocytes and
lymphocytes, appear as indurated areas in pathologic specimens; hence, the term
"sclerosis in plaques."
The disease can present in different forms, such as primary progressive, relapsing
remitting, relapsing progressive, and secondary progressive phenotypes.
MRI provides a roll in the diagnosis and assessment of treatment of MS with
demonstration of MS plaques within time or space.
MLF is a common ocular finding in MS and MRI may demonstrate a plaque in the region
of the MLF of the dorsal pons.
Personal Information
References
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