CASE 18463 Published on 04.03.2024

Radiological findings in amyotrophic lateral sclerosis: A case report

Section

Neuroradiology

Case Type

Clinical Case

Authors

Shrishail Adke, Ajith Varrior

Department of Radiology, Seth GS Medical College and KEM Hospital, Mumbai, Maharashtra, India

Patient

51 years, male

Categories
Area of Interest CNS ; Imaging Technique MR
Clinical History

A 51-year-old man presented with complaints of progressive dysarthria, dysphagia and weakness in the left hand since two years. There was atrophy of the intrinsic muscles of the left hand. There was spasticity with hypertonia in all the limbs. There was atrophy of the tongue with fasciculations.

Imaging Findings

Nerve conduction studies (NCS) and needle electromyography (EMG) revealed findings of lower motor neuron (LMN) abnormalities in three anatomic regions (bulbar, cervical and lumbosacral). An MRI of the brain was advised for evaluating the upper motor neuron features. There were T2/FLAIR hyperintensities along the motor tracts with diffusion restriction (Figures 1 and 2). There was a T2 hypointense band along the precentral gyrus with corresponding hypointensity in the susceptibility-weighted imaging (SWI) sequence (Figure 3). The tongue was hyperintense on non-fat saturated T1 weighted sequence with a drop in signal on fat suppression (Figure 4).

Discussion

ALS (Amyotrophic lateral sclerosis) is a progressive fatal neurodegenerative disorder with features of both UMN and LMN palsy. There is neuronal death involving the motor cortex, brainstem and the spinal cord.

ALS may present either as a bulbar or a spinal onset. In bulbar onset ALS, there is dysarthria and dysphagia. Pseudobulbar affect, such as uncontrollable bouts of laughter/crying, might be seen [1]. The spinal onset is more common and presents with limb weakness [2]. There are few atypical presentations, such as Mill’s syndrome (hemiplegic/asymmetric), flail-arm (man-in-barrel syndrome), flail-leg variant, pseudopolyneuritic variant [1].

The diagnosis of ALS is primarily based on the history and the clinical examination findings. MRI brain helps to rule out other differential diagnoses such as multiple sclerosis, vascular pathologies, neoplastic lesions, etc. Imaging of the spine may be advised to rule out myelopathy, radiculopathy or conus lesions [3]. Although there are no specific radiological findings in ALS, there are a few signs which might support the diagnosis of ALS, especially in the appropriate clinical context.

On conventional MRI, there is T2/FLAIR hyperintensity along the motor tracts (centrum semiovale, corona radiata, internal capsule, cerebral peduncles and the corticospinal tracts-CST), which are better appreciated on the coronal sections. This is known as the “wine glass” appearance. The loss of the myelin sheath after degeneration of the CST in ALS is responsible for the hyperintense signal of the tracts on T2 and FLAIR sequences. There might be areas of T2 hypointensity in the precentral cortex which show blooming on susceptibility-weighted imaging (SWI). It is known as the “motor band sign” [4]. A hyperintense signal in the tongue on a sagittal T1-weighted non-fat-saturated sequence with a signal drop on fat-suppressed sequences is known as bright tongue sign[5]. This represents fatty replacement of the tongue muscles due to denervation. These findings do not correlate with the clinical severity.

The voxel-based morphometry (VBM) can be used to detect regional atrophy [6]. Diffusion tensor imaging (DTI) shows alteration in the diffusion parameters along the CST, which are depicted as low FA (fractional anisotropy) [4,6]. MR spectroscopy shows reduced NAA (N-acetyl aspartate) levels with reduced NAA/Cho or NAA/Cr ratio. Perfusion studies showed hypoperfusion in the affected areas. Functional MRI depicts increased activity in the contralateral sensorimotor cortex and the supplementary motor cortex [3,6]. The high signal of the CST on T1 weighted SE MTC (spin echo magnetization transfer contrast) has a sensitivity of 80% and specificity of 100% [7].

Differential Diagnosis List
Primary lateral sclerosis
Amyotrophic lateral sclerosis
Wallerian degeneration
Metabolic encephalopathy (cobalamin deficiency)
Metabolic encephalopathy (hepatic encephalopathy)
Final Diagnosis
Amyotrophic lateral sclerosis
Case information
URL: https://eurorad.org/case/18463
DOI: 10.35100/eurorad/case.18463
ISSN: 1563-4086
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