CASE 14307 Published on 01.06.2017

Teaching case neuroradiology

Section

Neuroradiology

Case Type

Clinical Cases

Authors

Ibañez Caturla S, Morell Gonzalez G, Castillo Garcia A, Vazquez Sáez V, Bañon Garcia I

Hospital Universitario Virgen de la Arrixaca,
Radiodiagnostico;
Ctra. Madrid-Cartagena sn 3
0120 Murcia, Spain;
Email:santibacat@gmail.com
Patient

38 years, female

Categories
Area of Interest Neuroradiology spine, Neuroradiology brain ; Imaging Technique MR
Clinical History
A 38-year-old woman with initial left-hand weakness and progressive loss of strength involving both upper limbs and also left lower limb for about a year, accompanied by hyperreflexia, fasciculations and pyramidal symptoms. Muscular atrophy in hand and forearm.
No vibratory or pain sensibility loss. Intellectual functions were preserved.
Imaging Findings
Head MRI (with T1, T2, FLAIR, T2* and DWI sequences) revealed subtle bilateral T2 hyperintensities in the subcortical white matter, starting from the precentral gyrus (primary motor cortex) and descending along the corticospinal tract (both semioval centres, posterior limb of internal capsules, anterior midbrain and pons).
High signal is more evident in both internal capsules.
No signal anomalies were shown on the medulla.
Coronal T2 also demonstrates the increased signal along the corticospinal tract.

Spinal MRI (cervical, thoracic and lumbar spine) showed normal cord with no pathologic findings in this patient.
Discussion
Amyotrophic lateral sclerosis (ALS) is an idiopathic neurodegenerative disorder that affects upper and lower motor neurones [1]. It is the most frequent type of motor neuron disease, with an annual estimated incidence rate of 1-2 per 100000 people and prevalence around 5/100000 persons.
It normally affects people between 40-70 years of age, with slightly female predominance.
Most cases are sporadic; only around 5-10% of them are familial, with the mutation in the SOD1 gene the most common on chromosome 21q.
Histopathology reveals motor neuron loss with ubiquitin and neurofilament accumulation in degenerating motor neurons [2].

Clinically it is characterized by progressive muscular paralysis [1, 2], due to affectation of (normally) both upper and lower motor neurones (UMN and LMN):
- UMN includes Babinski sign, spasticity and hyperreflexia.
- LMN affectation includes muscle weakness (often asymmetric), atrophy, fasciculations and hyporeflexia.

ALS diagnosis was made based on "El Escorial" Criteria, which requires the presence of both upper and lower motor neuron signs (in our case, by clinical examination), and also progressive spread of signs to other regions.

As in our case, weakness in distal extremities (like hands and forearms) combined with spasticity and hyperreflexia are the most common findings.
Seldom affectation of the brainstem nuclei, with bulbar signs (tongue atrophy, dysphagia) may also be found, due to involvement of the hypoglossal nerve.

It is a progressive disease, with median survival from diagnosis 3-4 years and only 10% survival rate after 10 years.

MR IMAGING
As seen in our cases, bilateral T2 hyperintensities along the corticospinal tracts may be seen, but MRI can have no remarkable findings, and diagnosis should then be made based on other diagnostic resources [3].

MRI DIAGNOSTIC CLUES
At 3T MRI, corticospinal tracts are slightly hyperintense: this is a normal finding and should not be mistaken for pathology [4].

PD (proton density) should be used when this pathology is suspected, as T2 hyperintensity on the corticospinal tract may be specific if it is seen on corresponding PD.
DWI (diffusion-weighted imaging) may show hyperintensity as well (restricted diffusion).

Sometimes T2 hypointensity can be seen in the cortical grey matter of the precentral gyrus (it might be due to iron and heavy metals accumulation). FLAIR sequences are more sensitive but less specific for its detection [5].

MR Spectroscopy may show decreased NAA values and NAA ratios (NAA/Cr, NAA/Cho); magnetization transfer ratio (MTR) may show hyperintensity on T1 (rare but highly specific) [3, 5].

Spinal MRI may show hyperintense signals along the anterior and anterolateral aspects of the spinal cord on T2-weighted images [5].
Differential Diagnosis List
Amyotrophic lateral sclerosis (ALS)
Primary lateral sclerosis
Wallerian degeneration
Hepatic encephalopathy
Metabolic diseases involing corticospinal tract
Demyelinating and inflammatory diseases (MS
AIDS...)
HTLV Infection
Charcot-Marie-Tooth disease
Krabbe disease
Final Diagnosis
Amyotrophic lateral sclerosis (ALS)
Case information
URL: https://eurorad.org/case/14307
DOI: 10.1594/EURORAD/CASE.14307
ISSN: 1563-4086
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