This 34-year-old male presents with occipital headaches. Try to come up with your own diagnosis from the first image, then look at the duplicate image that includes arrows indicating the key findings.
This patient has Chiari I malformation.
Q1 – Which of the following is true? Chiari I malformation features:
(a) Male predominance
(b) Symptoms likely markedly increased with greater than 5 millimeters of ectopia
(c) Main indication for posterior fossa decompression is headache persisting greater than 1 year
(d) Variance of tonsilar position with patient age
Q2 – Associated skeletal abnormalities with Chiari I include all of the following except:
(b) Atlanto-occipital assimilation
(c) “Spit cord” syndrome
(e) Retroflexed dens
The diagnosis of Chiari I is controversial. Isolated tonsillar ectopia, while considered abnormal when greater than 4 millimeters, does not necessarily implicate Arnold-Chiari malformation as a diagnosis or the cause of symptoms. Other signs to support the diagnosis must include pegged-shaped tonsils, small occiput, proper symptoms (e.g. nystagmus, headaches, etc.), and especially syringohydromyella with or without the skeletal findings of Chiari I. These skeletal findings most prominently include:
It is critical to be sure low-lying tonsils are not due to sagging from intrathecal hypotension or downward pressure from intracranial hypertension. Decompression or lumbar puncture in such circumstance may be contraindicated.
Up to 30 percent of patients with tonsillar ectopia between 5 and 10 millimeters may not be symptomatic. If the patient is not symptomatic, they do not require treatment. Syrinx is the only widely accepted definitive indication for surgical treatment. Non-stereotypic headaches are not a surgical indication by themselves.
Patients with Chiari II are characterized by lumbar dysraphism, specifically myelomeningocele or lipomyelomeningocele. Medullary kinking or Z-deformity at the craniocervical junction with descent not only at the tonsils but also the medulla is seen in Chiari II.
A1 – (d) Variance of tonsilar position with patient age
A2 – (c) “Spit cord” syndrome
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1. Elster et. al. Radiology 1992; 183 (2).