"Ears of the lynx" sign in hereditary spastic paraplegias is not always the same!

Sinal da orelha do lince nas paraplegias espásticas hereditárias nem sempre é o mesmo!

Hereditary spastic paraplegias (HSPs) are a heterogeneous group of genetic disorders featuring lower extremity spasticity and weakness. The "ears of the lynx" is a magnetic resonance imaging (MRI) sign that refers to degeneration of the forceps minor. Despite mimicking acquired conditions, like ependymitis granularis, it is considered a hallmark of some HSPs, such as types 15 and 11.¹ However, there were other types reported to have this sign,²,³ particularly when accompanied by atrophy of the anterior portion of the corpus callosum.

A 34-year-old man with walking disturbance presented with spastic paraparesis in the lower limbs, cerebellar ataxia, and sensory–motor polyneuropathy. A brain MRI was performed (Figure 1), and the exam showed a biallelic pathogenic mutation in spastic paraplegia type 7 (c.376 + 1G > T / c.1369C > T / ENST00000645818).

Figure 1
(A) Axial fluid attenuated inversion recovery (FLAIR), with white arrow showing the "ears of the lynx" sign and (B) Sagittal T1 showing cerebellar atrophy. Both (C) and (D) show a normal examination with an important differential diagnosis of "Ears of the lynx" signal, ependymitis granularis, which is usually more rounded and subtle.

We recommend brain MRIs to search for this sign in all suspected cases of HSP. However, it is important to interpret with caution when finding "ears of the lynx" in isolation, with absence of corpus callosum atrophy.

References

• ¹ Faber I, Servelhere KR, Martinez ARM, D’Abreu A, LopesCendes I, França MC Jr. Clinical features and management of hereditary spastic paraplegia. Arq Neuropsiquiatr 2014;72 (03):219–226
• ² Sáenz-Farret M, Lang AE, Kalia L, et al. Spastic Paraplegia Type 7 and Movement Disorders: Beyond the Spastic Paraplegia. Mov Disord Clin Pract (Hoboken) 2022;9(04):522–529
• ³ Agarwal A, Oinam R, Goel V, et al. "Ear of the Lynx" Sign in Hereditary Spastic Paraparesis (HSP) 76. Mov Disord Clin Pract (Hoboken) 2022;10(01):120–123

Edited by

• Editor-in-Chief: Hélio A. G. Teive.
  Associate Editor: Antonio José da Rocha.

Publication Dates

• Publication in this collection
  23 Aug 2024
• Date of issue
  2024

History

• Received
  02 Feb 2024
• Reviewed
  22 Apr 2024
• Accepted
  01 May 2024