Supplementary material
Formal vestibular assessment
Vestibular failure was defined as a gain ratio of (angular velocity of eye
movement)/(angular velocity of head movement) 80ms after onset of head impulse of
less than 0.79 (2 standard deviations less than mean in our 60 historical controls aged
20-80 years) (Mossman et al., 2012) or by peak slow phase velocity of the nystagmus
on bithermal caloric testing of less than 20°/s summated over the four irrigations
(Kim et al., 2011).
Autonomic assessment
Autonomic testing
The protocol used for autonomic function assessment was adapted from Ewing et al
for the diagnosis of diabetic autonomic neuropathy (Ewing and Clarke 1982; Ewing et
al., 1985). The tests assessed both parasympathetic and sympathetic functions and a
detailed description of the procedures is provided below.
Parasympathetic function
Each patient had continuous ECG monitoring for heart rate variation during Valsalva
manoeuvre, deep breathing and on standing.
Valsalva ratio
For the Valsalva manoeuvre each patient was asked to blow forcefully to maintain a
pressure equivalent to 40 mmHg on a sphygmomanometer for 15 seconds. The patient
was allowed to rest for 1 minute before repeating the Valsalva manoeuvre. This was
performed three times and the R-R intervals during the Valsalva manoeuvre and in the
rest period were measured. The Valsalva ratio was calculated by dividing the
maximum R-R interval following Valsalva manoeuvre with the minimum R-R
interval during Valsalva. The mean ratio of the three attempts was calculated. (Ewing
and Clarke 1982; Ewing et al., 1985)
Heart rate variation during deep breathing
During this manoeuvre the patient was asked to breathe deeply over 10 second cycles
for one minute with continuous ECG rhythm recording. The maximum and minimum
R-R intervals during each cycle were recorded to enable calculation of the maximum
and minimum heart rates. The heart rate in beats per minute was calculated by
dividing 60 by the R-R interval. The difference between maximum and minimum
heart rates during each cycle was calculated and the mean difference of the six cycles
was obtained.
Heart rate variation on standing
The patient was asked to stand up from a resting supine position without aid. The
shortest R-R interval around the 15th heart beat (R-R 15) and the longest R-R interval
around the 30th heart beat (R-R 30), after assuming the standing position, were
measured. The 30:15 ratio was calculated as R-R 30 / R-R 15.
Sympathetic function:
Postural blood pressure and blood pressure response to handgrip were measured.
Postural blood pressure was measured after the patient had lain supine for 2 minutes
and after at least 1 minute of standing up. The systolic blood pressure difference
between lying and standing was measured. If two or more readings were obtained the
average difference was recorded.
To assess blood pressure response to handgrip, the patient was asked to grip at 30% of
maximum on a sphygmomanometer bulb and to maintain this for 5 minutes. Three
resting blood pressure measurements were obtained prior to handgrip. During
handgrip blood pressure was measured at one-minute intervals. Blood pressure
response to handgrip was measured as the difference between the mean pre-handgrip
diastolic blood pressure and the maximum diastolic blood pressure obtained during
handgrip.
Interpretation of autonomic tests
Each autonomic test (other than the Valsalva ratio which does not have a borderline
range) has a defined normal, borderline and abnormal range as described in Ewing
and Clarke’s classification of autonomic test results (Ewing and Clarke 1982; Ewing
et al., 1985). We ascribed a score of zero for normal, one for borderline and two for
abnormal. With minor modification to the Ewing classification, we defined definite
parasympathetic dysfunction as a score of ≥ four (equivalent to at least two abnormal,
or one abnormal and two borderline results) and definite sympathetic dysfunction as a
score of ≥ two (at least one abnormal or two borderline) results. In a series of 71
normal controls studied by Ewing et al (age range 16 - 69) only one control subject
had an abnormal result using this battery of tests (one subject had a 30:15 ratio of
1.0). (Ewing et al., 1985)
Imaging analysis for focal cerebellar atrophy and association with
downbeat nystagmus
Methods:
The neuroradiologists assessed four cerebellar areas for atrophy: the ventral vermis,
the dorsal vermis and the cerebellar hemisphere crus I – which have been identified as
showing atrophy in CANVAS (Szmulewicz et al., 2011) - and the floccular complex
which has been associated with DBN (Pierrot-Deseilligny and Milea 2005). The
vermis and flocculus were assessed using freehand outlining of the areas and standard
MRI software to calculate the enclosed area, following the method of Webb et al.
(Webb et al., 2009) For crus I we used the ratio on sagittal T1 at the level of the
flocculus of maximum craniocaudal thickness of crus I: maximum thickness of
horizontal fissure (supplementary fig. 1). Inter-rater reliability of MRI measurements
was assessed using the ICC (intraclass correlation coefficient).
Results:
Twenty-three scans were available for assessment of focal atrophy. There was
reasonable inter-rater agreement for measurements of the anterior, dorsal and inferior
vermis and for the ratio of crus I to the horizontal fissure (ICC coefficients 0.78, 0.70,
0.68, 0.65, respectively), but the measurement of the area of the flocculus was not
reliable (ICC coefficient 0.34), likely due to its small size and highly irregular outline.
Sixteen of these patients had DBN and seven did not. Average measured size of all
four regions was slightly smaller in the DBN subgroup, but no clear association with
atrophy of any particular area of the vermis or crus I was seen (p values for anterior
vermis, 0.11; dorsal vermis, 0.47; inferior vermis, 0.36; and crus I, 0.15). Generally
there was increased atrophy with increased disease duration, but this was only
statistically significant for crus I atrophy (p < 0.001). There was no correlation
between the degree of atrophy and age.
References:
Ewing, D. J. and Clarke, B. F. (1982), 'Diagnosis and management of diabetic
autonomic neuropathy', Br Med J (Clin Res Ed), 285 (6346), 916-8.
Ewing, D. J. et al., (1985), 'The value of cardiovascular autonomic function tests: 10
years experience in diabetes', Diabetes Care, 8 (5), 491-8.
Kim, S. et al., (2011), 'Bilateral vestibulopathy: clinical characteristics and diagnostic
criteria', Otol Neurotol, 32 (5), 812-7.
Mossman, B. et al., (2012), 'Normal horizontal VOR gain with video-oculography
(EyeSeeCam VOG). ', Poster presented at: the 27th Barany Society Meeting,
Uppsala, Sweden June 10-13.
Pierrot-Deseilligny, C. and Milea, D. (2005), 'Vertical nystagmus: clinical facts and
hypotheses', Brain, 128 (Pt 6), 1237-46.
Szmulewicz, D. J. et al., (2011), 'Sensory neuropathy as part of the cerebellar ataxia
neuropathy vestibular areflexia syndrome', Neurology, 76 (22), 1903-10.
Webb, S. J. et al., (2009), 'Cerebellar vermal volumes and behavioral correlates in
children with autism spectrum disorder', Psychiatry Res, 172 (1), 61-7.
Figure Legend
Figure 1: 1a - Representative mid-sagittal measurement of vermal subregions: lobules
regions I – V (superior enclosed region), VI-VII (mid-posterior region), VIII-X
(inferior region). 1b – Measurement of the flocculus and relative atrophy of Crus I as
measured by ratio calculated by maximum Crus I craniocaudal thickness / maximum
thickness of horizontal fissure.