Downbeat nystagmus and progressive ataxia in adults: consider Chiari malformation type 1

Downbeat nystagmus (DBN) is present in between 4 and 6% of patients with Chiari malformation type 1 (CM1). It is present in primary gaze and is characterized by a pathological phase which drifts the eyes in the upward direction followed by a downward quick-phase.[1] [2] [3] Chiari malformation type 1 is one of the most prevalent craniocervical junction abnormalities[4] and is more frequent in Northeastern Brazilians, due to pre-historic ancestors (previously thought to be caused by the Dutch colonization).[5] The herniation of cerebellar tonsils through the foramen magnum is radiologically characterized by the distance between the apex of the odontoid and Chamberlain line of at least 5 mm.[6]

We present a four-case series of CM1 patients who developed progressive cerebellar ataxia and DBN. Brain magnetic resonance imaging (MRI) revealed the abnormal projected cerebellar tonsils. Evaluation of the posterior fossa through brain imaging looking for structural abnormalities such as CM1 is mandatory in cases of progressive ataxia combined with DBN, headache, and pyramidal signs ([Video 1] and [Fig. 1]).

Figure 1 (Case A-D) Cranio-cervical MRI showing Chiari malformation type 1 in the four patients with progressive ataxia and downbeat nystagmus, which is defined by herniation of cerebellar tonsils through the foramen magnum (located at least 5 mm below this structure) (arrows).

Video 1 Video of the patients with progressive ataxia and downbeat nystagmus related to Chiari malformation type 1.

Conflict of Interests

The authors have no conflict of interest to declare.

Note

The patients have consented with the publication of the manuscript and its accompanying figures and videos.

Authors' Contributions

BKM: data curation, formal analysis, investigation, methodology, writing – original draft; TCV: conceptualization, formal analysis, methodology, project administration, validation, visualization, writing – original draft, writing – review & editing; FMRF: data curation, formal analysis, investigation, methodology; OGPB: conceptualization, data curation, formal analysis, investigation, methodology, project administration, supervision, validation, visualization, writing – original draft, writing – review & editing; JLP: conceptualization, data curation, formal analysis, methodology, supervision, writing – original draft, writing – review & editing.

• References

• 1 Milhorat TH, Chou MW, Trinidad EM. et al. Chiari I malformation redefined: clinical and radiographic findings for 364 symptomatic patients. Neurosurgery 1999; 44 (05) 1005-1017
• 2 Wagner JN, Glaser M, Brandt T, Strupp M. Downbeat nystagmus: aetiology and comorbidity in 117 patients. J Neurol Neurosurg Psychiatry 2008; 79 (06) 672-677
• 3 Joaquim AF. Severe Cerebellar Degeneration and Chiari I Malformation - Speculative pathophysiology based on a systematic review. Rev Assoc Med Bras 2020; 66 (03) 375-379
• 4 Fernández AA, Guerrero AI, Martínez MI. et al. Malformations of the craniocervical junction (Chiari type I and syringomyelia: classification, diagnosis and treatment). BMC Musculoskelet Disord 2009; 10 (Suppl 1, Suppl 1) S1
• 5 Carvalho A, Bertholdo DB. Craniocervical junction abnormalities in northeast Brazilian population. Arq Neuropsiquiatr 2017; 75 (07) 410-411
• 6 Frade HC, França CCNL, Nascimento JJCD, Holanda MMA, Silva EJD, Araújo SA. Cranio-vertebral transition assessment by magnetic resonance imaging in a sample of a northeast Brazilian population. Arq Neuropsiquiatr 2017; 75 (07) 419-423

Publication History

Received: 23 December 2022

Accepted: 16 March 2023

Article published online:
29 September 2023