Evans RW. Incidental Findings and Normal Anatomical Variants
on MRI of the Brain in Adults for Primary Headaches. Headache. 2017
May;57(5):780-791.
Abstract
When MRI scans of the brain are obtained for evaluation of
primary headaches in adults, incidental findings are commonly present. After a
review of the prevalence of incidental findings and normal anatomical variants,
21 types are presented.
_________________________________________________________________________
From the article
About 90% of all headaches are the primary type where MRI
scans of the brain will not reveal any pathology responsible for headaches. MRI
scans are frequently done for primary headaches for a variety of reasons
including the following: secondary pathology; at the patient's or family's
request; to reassure the patient, “our stubborn quest for diagnostic
certainty;” faulty cognitive reasoning;
the medical decision rule where it is better to impute disease than to risk
overlooking it; busy practice conditions where tests are ordered as a shortcut;
financial incentives; professional peer pressure where recommendations for
routine and esoteric tests are expected as a demonstration of competence; and
medicolegal concerns. Incidental findings are common, often revealing benign
pathology which may cause concern of the patient. Normal anatomical variants
are also common. Definitions may differ
among investigators as some may classify normal anatomical variants as
incidental findings while others may not.
CASE HISTORY
Case 1
This is a 32-year-old male with a history of increasingly
frequent episodic migraine. MRI of the brain was normal except for a 7 mm
pineal cyst. Another MRI of the brain 5 years later for chronic migraine showed
no change in the size of the cyst.
Case 2
This is a 27-year-old male, the brother of case 1, with a
history of headaches consistent with migraine without aura since childhood.
Headaches have increased to twice a week in frequency. Past medical history is
negative. Neurological examination is normal. Magnetic resonance imaging (MRI)
of the brain shows a left anterior cranial fossa arachnoid cyst measuring
1.2-cm anteroposterior by 1.6-cm transverse by 1.5-cm craniocaudad without
significant parenchymal compression. He is placed on a triptan with a good
response….
There have been a number or studies which report IF in
normal volunteers with the prevalence of clinically significant
neuropathologies occurring in 2-8% of the general population.
In a meta-analysis of 16 studies of 19,559 people with a
range of 1-97 years without neurological symptoms who underwent MRI of the
brain with or without contrast for research purposes or for occupations,
clinical, or commercial screening, the overall prevalence of IF was 2.7% (4.3%
in studies where participants underwent at least one high resolution MRI
sequence versus 1.7% in studies using only low resolution sequences). White
matter hyperintensities, silent brain infarcts, brain microbleeds, and
anatomical variants were not included. The following IF and prevalences (%) were
found: neoplasia, 0.7 (meningioma, 0.29; pituitary adenoma, 0.15; low grade
glioma, 0.05, acoustic neuroma, 0.03; lipoma, 0.04; epidermoid, 0.03);
structural vascular abnormalites, 0.56 (aneurysm, 0.35; cavernous malformation,
0.16; arteriovenous malformation 0.05); inflammatory lesions, 0.09 (definite
demyelination, 0.06; possible demyelination, 0.03); cysts, 0.54 (arachnoid
cysts, 0.5; colloid cyst, 0.04), Chiari I malformation, 0.24; hydrocephalus,
0.10; and extra-axial collection, 0.04.
In a study of 206 healthy volunteers ages 9-50 years (mean
25.68 years) on a 3-tesla MRI scanner, 19% had incidental findings. IF without clinical importance were present in
9% as follows: signal abnormalities, 4%; pineal cysts < 1 cm, 3%; and mega
cisterna magna, 1%. IF with clinical importance were present in 10% as follows:
intrasellar abnormalities, 6%; pineal cysts >1 cm, 2%; cavernomas, 1%;
arteriovenous malformations, 1%; multiple white matter lesions, 1%; Chiari
malformation, 1%; subependymal heterotopia, .5%; and multiple sinusoidal
polpys, 1%.
In a study of 203 healthy volunteers ages 18-35 years (mean
21.9 years) on a 1.5-tesla MRI scanner, 30.5% had variations of the norm
including the 3 most common as follows: pineal gland cyst, 6.1%; widened
bifrontal subarachnoid space, 6.1%; and Rathke cleft cyst, 3.9%.[8] IF of the
brain were found in 9.4% with occasional/not important white matter lesions,
4.4% and Chiari I malformations, 1%. In 180 participants, the upper head and
neck region were evaluated, finding 3.3% with variants of the normal (most
common hypoplastic frontal or maxillary sinus) and 36.7% with abnormal findings
(most common sinonasal retention cyst or polyp, 10%; isolated mucosal swelling,
6.1%; pharyngeal or parotid lymphadenopathy, 5%; and cystic lesion in the
parotid gland, 1%.
No comments:
Post a Comment