LETTER TO THE EDITOR
|Year : 2020 | Volume
| Issue : 6 | Page : 821-823
“Motor band sign” in susceptibility-weighted imaging in motor neuron Disease
Arvind N Prabhu, Lakshmi Manasa Sajja
Department of Neurology, Kasturba Hospital, KMC, MAHE, Manipal, Karnataka, India
|Date of Submission||07-May-2019|
|Date of Acceptance||31-May-2019|
|Date of Web Publication||02-Aug-2019|
Dr. Arvind N Prabhu
Department of Neurology, Kasturba Hospital, Manipal Karnataka
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Prabhu AN, Sajja LM. “Motor band sign” in susceptibility-weighted imaging in motor neuron Disease. Ann Indian Acad Neurol 2020;23:821-3
A 70-year-old male with hypertension of 15 years duration and recent diabetes presented with insidious onset progressive asymmetric stiffness and weakness of left lower and left upper limb of 16 months duration and right upper limb since 3 months. Examination showed left more than right spasticity with brisk reflexes, clonus and extensor plantar response. Other higher mental function, cranial nerve, sensory and cerebellar examination were normal. Nerve conduction studies, EEG, MRI spine were normal. Hematological and Biochemical tests were normal including serum electrophoresis, serum electrolytes, parathyroid hormone, thyroid panel and creatinine kinase levels. At the same time, tumor markers were negative. Paraneoplastic antibodies (anti-Hu, anti-Ri, anti-Yo, anti-CV2, anti-PNMA 2, anti-PNMA1, anti-amphiphysin, anti-PCA-2, anti-SOX1, anti-Tr, anti-MAG, anti-ZIC4, anti-titin, anti-recoverin, anti-myelin) were negative. PET scan for malignancy screening was normal. EMG showed neuropathic pattern with no evidence of active denervation or reinnervation. There was no family history of similar complaints. A differential of Primary Lateral Sclerosis (PLS) was considered, but at present, patient does not fulfil the Pringle/Gordon criteria for duration of illness 3/4 years for diagnosis of PLS. Therefore, a diagnosis of Primary UMN dominant Amyotrophic Lateral sclerosis (ALS) was made, as all other differentials were excluded.
PLS is considered as Motor Neuron Disease type (MND) which exclusively affects Upper Motor Neurons (UMN) and also as variant of ALS. There is no reliable para clinical marker for UMN involvement in MND/PLS/ALS. Also, there is no definite neuroimaging technique for demonstrating UMN involvement.
Increased T2 signal changes have been reported along the course of corticospinal tracts from the subcortical precentral gyrus through the centrum semiovale, posterior limb of internal capsule, cerebral peduncles, pons, medullary pyramids, and anterior and lateral corticospinal tracts of the spinal cord. These magnetic resonance changes have been thought to represent corticospinal degeneration. However, they are not sensitive or specific for MND/PLS/ALS and may be associated with normal aging.
Susceptibility-weighted imaging (SWI) is a new high-resolution, three-dimensional gradient echo MR imaging (MRI) technique that may be more effective in detecting changes in motor cortex, and thus likely provide supportive evidence of UMN involvement. This gradient echo sequence that uses magnitude and phase data both separately and added together after appropriate filtering to enhance the paramagnetic properties that underlies tissue susceptibility. It has been shown to be very sensitive to iron in the form of hemosiderin, ferritin, and intracellular methemoglobin and deoxyhemoglobin.
The striking feature in SWI in our patient was exclusive involvement of the bilateral motor cortex (Brodmann's area 4 or primary motor cortex M1) in a band-like fashion “Motor Band Sign” [Figure 1] with higher hypo intensity on right motor cortex compared to left corresponding with the clinical severity. The mechanisms for this at present not clear. However, it was postulated that perhaps microglia accumulate this iron as they phagocytose degenerating neurons from the primary motor cortex. Hypointensity in grey matter of precentral gyrus in SWI and T2 is presumably related to iron accumulation, proportionally to severity of UMN impairment.
|Figure 1: SWI axial shows asymmetric blooming and thinning in precentral gyrus (right more than left)|
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Previous case reports, described a total of 4 cases of ALS and one case of PLS with similar imaging findings of motor band sign as isolated finding. In one more case report, retroviral disease with progressive multifocal leukoencephalopathy (PML) patient had similar sign. However, there were other extensive white mater hyper intensities consistent with PML in this case.
A specific pattern of motor cortex involvement like in this case might be an imaging clue to UMN involvement in MND. Larger prospective studies will be needed to determine the incidence, sensitivity, and specificity of the motor band sign in MND and its usefulness as prognostic indicator.
Dr. Prof (Brig) S P Gorthi, Professor and Head of Department, Department of Neurology, Kasturba Hospital, KMC, MAHE, Manipal.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
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