J Neurol Neurosurg Psychiatry 1998;64:221–226 221 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.64.2.221 on 1 February 1998. Downloaded from Symptomatic tonsillar ectopia Kazuhide Furuya, Keiji Sano, Hiromu Segawa, Katsuhisa Ide, Hidehiko Yoneyama Abstract hydrocephalus.12Recently, many authors have Objective—To determine if slight descent used the term “Chiari type I malformation” to of the cerebellar tonsils (< 5 mm below the describe tonsillar herniation with and without foramen magnum; tonsillar ectopia) may hydrocephalus, resulting in confusion regard- cause surgically treatable symptomatol- ing the meaning of this term.347910We identi- ogy. fied through neurotological examinations sev- Methods—A consecutive series of nine eral cases of descent of the cerebellar tonsils to symptomatic patients with tonsillar ecto- less than 5 mm below the foramen magnum pia seen between December 1990 and (tonsillar ectopia) in which the patients experi- March 1993 are reported on. The same enced medically intractable dull pain in the number of age and sex matched controls occipital area and cerebellovestibular dysfunc- were selected at random from outpatients. tion symptoms. These patients underwent pos- Twelve asymptomatic subjects with tonsil- terior fossa decompression surgery, following lar ectopia were found among 5000 people which their clinical symptoms improved. In between January 1991 and March 1996. this report, we propose implications of chronic Diagnosis of tonsillar ectopia was based intractable occipital dull pain and cerebello- on midsagittal MRI. vestibular dysfunction in patients with tonsillar Results—Patients presented mainly with ectopia. chronic intractable occipital dull pain, vertigo, and dysequilibrium. In all pa- Subjects and methods tients MRI showed normal brain structure GENERAL POPULATION STUDY except for tonsillar ectopia (-2.9 (SD 0.8) We analysed 5000 subjects to check the degree mm), which has historically been thought of descent of the cerebellar tonsils below the to be of no clinical relevance. In the level of the foramen magnum between January control group the tonsilar position was 1991 and March 1996. They were people who +2.1 (SD 2.8) mm (p<0.01). Neurotologi- wished to check their neurological status. We cally abnormal findings were detected found 12 subjects with asymptomatic tonsillar with a monaural speech integration test ectopia among them (0.24%). There were four (100%), eye tracking test (56%), optoki- men and eight women ranging in age from 24 netic nystagmus test (89%), and visual to 60 years. suppression test (67%) which strongly suggested a CNS lesion. In accordance PATIENT CLINICAL CHARACTERISTICS with the results of MRI and precise neuro- The subjects were nine women, aged 19 to 65 tological examination, posterior fossa de- years, who had been admitted to the hospital compression surgery was carried out, between December 1990 and March 1993. http://jnnp.bmj.com/ Table 1 shows the clinical characteristics of Department of followed by improvement of preoperative symptoms and less severity of neuroto- these patients, all of whom underwent Neurosurgery neurological evaluation before undergoing sur- K Furuya logical abnormalities in all patients. gery. The mean duration of follow up was 3.2 K Sano Conclusion—Tonsillar ectopia could cause H Segawa neurological symptoms in small popula- years. K Ide tions, which were surgically treatable. TERMINOLOGY Department of Neurotological assessment was necessary Terminology regarding descent of the cerebel- on October 1, 2021 by guest. Protected copyright. to verify the aetiological relation between Neurotology, Fuji lar tonsils below the foramen magnum as Brain Institute and tonsillar ectopia and various symptoms. Hospital, Sugita detected by MRI was according to that established in earlier publications.11–13 Briefly, 270–12, Fujinomiya (J Neurol Neurosurg Psychiatry 1998;64:221–226) City, Shizuoka tonsillar herniation of between 1 mm and 5 Prefecture 418, Japan Keywords: Chiari type I malformation; magnetic mm is termed tonsillar ectopia. The criterion H Yoneyama resonance image; neurotological examination; tonsillar for the diagnosis of a Chiari malformation is ectopia tonsillar displacement to 5 mm or more below Correspondence to: 11 Dr Kazuhide Furuya, the foramen magnum. National Institute of Neurological Disorders and Chiari Type I malformation is a well known MRI AND DATA ANALYSIS Stroke, Stroke Branch Building 36, Room 4A03, disease involving caudal descent of the cere- All patients underwent preoperative MRI Bethesda, Maryland bellar tonsils and is occasionally associated which was performed using a 0.5T unit 20892–4128, USA. with syringomyelia.1–9 In 1891 and 1895, (Toshiba TCT 70A-II, Tokyo, Japan). A sagit- Telephone 001 1 301 496 12 6579; Fax 001 1 301 402 Chiari precisely described this malformation tal multisection sequence (repetition time 2769. and related ones, which he designated type II, (ms)/echo time (ms)=250/14) with sections 5 type III1, and type IV2 malformation. He mm thick was performed. Received 22 November 1996 speculated that this condition, which is a Nine age and sex matched patients consid- and in revised form 15 May 1997 herniation of the posterior fossa contents below ered not to have disorders that would aVect Accepted 5 June 1997 the level of the foramen magnum, is caused by the position of the cerebellar tonsils, were 222 Furuya, Sano, Segawa, et al J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.64.2.221 on 1 February 1998. Downloaded from Table 1 Clinical characteristics of nine patients with symptomatic tonsillar ectopia Preoperative symptoms and signs Patient Occipital Ataxic unstable Duration of Follow up Position of No Age/sex headache Vertigo gait Numbness symptoms period (y) tonsils* 1 65/F + + − − 15 y 4.5 −3 mm 2 56/F + + − − 4 y 4.5 −3 mm 3 51/F + + + + 2 y 2.2 −1.5 mm 4 64/F + + − − 1 y 4 −2 mm 5 19/F + + + + 9 months 4 −3 mm 6 56/F + + − − 2 months 2.1 −3 mm 7 61/F + − − + 6 months 3 −3 mm 8 24/F + − + − 2 y 2.7 −4 mm 9 59/F + − − − 6 y 2.2 −4 mm * The level of the foramen magnum is defined as the basion-opisthion line as detected by MRI. The perpendicular distance from the basion-opisthion line to the tip of cerebellar tonsils was measured. − = Below the level of the basion-opisthion line. randomly sampled and subjected to MRI. The subjects and is considered abnormal when it is extent of tonsillar herniation was measured in less than 40%.23 24 Postoperative neurotological the midsagittal plane. The bottom of the assessment at two months after surgery was foramen magnum was determined by drawing performed for all patients in the same manner a line from the lowest cortical bone (visualised by the same author. as a lack of signal) at the inferior tip of the cli- vus (basion) to the lowest cortical bone at the Results inferior border of the posterior lip of the The mean age of the 12 subjects with asympto- 14–16 foramen magnum (opisthion). Data are matic tonsillar ectopia was 49 and that of the expressed as means (SD). Statistical evaluation nine patients with symptomatic tonsillar ecto- was performed by unpaired Student’s t test to pia at the time of diagnosis was 50. This is compare the data between two groups. Prob- higher than the reported mean age of patients ability values of p<0.05 were considered to be with Chiari type I malformation.3 5–8 15 All of significant. the nine patients were women. The duration of symptoms in these nine patients varied from NEUROTOLOGICAL EXAMINATIONS two months to 15 years, with a mean of 3.5 Preoperative neurotological examination was years. The most common symptom was pain in performed for all patients by one of us (HY) to the occipital area or the posterior cervical assess the function of the cerebellovestibular region, similar to findings in other studies.56In system. Firstly, the possibility of conductive or particular, all of the patients with symptomatic sensorineural hearing loss was ruled out. tonsillar ectopia had this symptom. The next Brainstem auditory evoked potentials (BAEPs) most common symptom was vertigo, followed were recorded (90 dB, 2.0 kHz click stimula- by unstable gait and numbness of the limbs. tion). The neurotological examination con- The mean tonsillar position in the control sisted of two parts, one of which was speech group was +2.1 (SD 2.8) mm, whereas it was audiometry, subdivided into a speech discrimi- −2.9 (SD 0.8) mm in the patients (p<0.01). nation test and a monaural speech integration Tonsillar displacement below the foramen http://jnnp.bmj.com/ test.17 18 In the other, equilibrium was examined magnum did not exceed 5 mm in any of the using spontaneous nystagmus evaluation, eye patients. Although an angulated or peg-like tracking test (ETT; 0.33 Hz, 10°/s),19 optoki- configuration of the tonsils was also character- netic nystagmus test (OKN test; acceleration istic of tonsillar herniation,14 none of the 4°/s2) including vertical upward and downward patients showed such a deformity of the tonsils. OKN and horizontal optokinetic pursuit In addition, none of the patients showed syrin- (OKP) test,19–21 and visual suppression test.22–24 gomyelia. ETT patterns were classified according to the Table 2 shows the preoperative neurological on October 1, 2021 by guest. Protected copyright. system described by Benitez,19 as follows: findings. Four of the nine patients had pattern I, smooth sinusoidal tracing; pattern II, vibratory sensory disturbance. Superficial sen- a few intermittent non-nystagmic movements sation was normal in all patients. Patients who every few seconds, superimposed on a sinusoi- complained of numbness did not always have a dal curve; pattern III, fast saccadic movements vibratory sensory disturbance. Three of the superimposed on an otherwise sinusoidal nine patients had truncal ataxia, two had limb curve; pattern IV, loss of the sinusoidal curve due to an eye movement imbalance.