Letters to the Editor

gramme. This is in keeping with the tremor of
other body parts, for example the wing-
beating arm tremor of Wilson's disease and
task-specific tremors such as writing and
other occupational tremors.3
We have examined clinically, three other

patients with clear dystonic head tremor in
whom head tremor was altered by the posi-
tion of the head in the anterior-posterior
plane. In none of the others could we
demonstrate a vestibular (otolith) mecha-
nism. Despite these negative observations for
a clear otolith influence upon head tremor
electrophysiological measurements have
shown that otolith spinal reflexes may be
modulated by both head and body position.6
Thus there still remains the possibility that a
change in head or body position may in itself
modify vestibular influences upon body
movement.

S MOSSMAN
L CLEEVES
L FINDLEY

MRC Human Movement and Balance Unit,
Section of Neuro-otology,

National Hospital for Neurology and Neurosurgery,
London, UK

Correspondence to: Dr Mossman, Department of
Neurology, Wellington Hospital, Private Bag, Wel-
lington South, Wellington, New Zealand.

1 Denny-Brown D. Clinical symptomatology of
diseases of the basal ganglia. In: Vinken P,
Bruyn G, eds. Handbook of clinical neurology,
vol 6. Amsterdam: North Holland Publishing
Co, 1968:133-9.

2 Bronstein A, Rudge P, Beechey A. Spasmodic
torticollis following unilateral VIII nerve le-
sions: neck EMG modulation in response to
vestibular stimuli. J Neurol Neurosurg Psy-
chiatry 1987;50:580-6.

3 Cleeves L, Findley L, Marsden D. Odd tremors.
In: Marsden D, Fahn S, eds. Movement
disorders 3. Butterworths (In Press).

4 Podivinsky F. Torticollis. In: Vinken P, Bruyn G,
eds. Handbook of clinical neurology, vol 6.
Amsterdam: North Holland. 1968:567-603.

5 Gresty M, Barratt H, Page N, Rudge P. Analysis
of downbeat nystagmus. Otolith vs semi-
circular canal influences. Arch Neurol
1986;43:52-55.

6 Dieterich M, Brandt T, Fries W Otolith func-
tion in man. Brain 1989;112:1377-92.

Probable cases of Mast syndrome in a
non-Amish family

Complicated forms of hereditary spastic
paraplegia are rare. A 58 year old Flemish
woman was admitted with a clinical picture
of slowly progressive spastic paraplegia, dys-
arthria, presenile dementia and mild atheto-
sis.
At the age of 16 her gait became shuffling.

Before the age of 30 she used a walking stick,
since the age of 35 years she has needed a
walking frame and from the age of 40 she has
become more wheelchair bound. During the
third decade (maybe earlier) dysarthria, apa-
thy and negativism appeared. Towards her
45th year, urinary incontinence began. On
admission, aged 48, significant bradyphrenia
and comprehension difficulties were noted
and during the following years she presented
a further mental deterioration. She is now
bedridden and her speech restricted to rare,
usually inappropriate, single syllable answers,
which are sometimes repeated. She has diffi-
culty swallowing fluids. She often shows
spontaneous repeated slow turning of the
head to the right and left and mild tortuous
movements of the shoulders. Except for a
divergent strabismus there are neither oculo-
motor abnormalities, nor fundoscopic
anomalies. There is a slight bilateral facial
weakness. The fine motor hand skills are lost

, = proband; * = birth order in this sibship
is uncertain

Figure Pedigree

without clear paresis of the upper limbs. The
strength of leg muscles measures about 1 to
2/5. There were neither sensory deficits nor
cerebellar signs. Deep tendon reflexes in the
upper limbs were increased slightly. Knee
jerks were unusually brisk and without clo-
nus; ankle jerks were decreased. Plantar
responses were extensor. Snout reflex and
bilateral palmomental reflexes were present
whilst corneomandibular reflexes were
absent.
The following laboratory investigations

showed no significant abnormalities: routine
blood examination (except for intermittent
elevation of glucose with normal haemoglo-
bin A1C ), creatine kinase, copper, lipids,
very long chain fatty acids ratios C24/C22
and C26/C22, vitamin E, vitamin B1 2,
folate, cortisol, adrenocorticotropic hor-
mone, thyroid hormones, arylsulfatase A and
hexosaminidase A + B; the CSF protein was
590 mg/l with normal electrophoretic pat-
tern.
The EEG showed mild general slowing.

Nerve conduction studies and needle electro-
myography showed a mild axonal polyneur-
opathy. The somato-sensory evoked
potentials demonstrated a slightly prolonged
central conduction time. An electrocardio-
gram was normal. MRI of the brain showed
diffuse cortico-subcortical atrophy, periven-
tricular hyperintensities, thin corpus callo-
sum and less marked atrophy of the
brainstem and cerebellum. Light microscopic
and electron microscopic examination of
conjunctiva and skin showed some mem-
branous cytoplasmic body-like inclusions
(Professor J J Martin, Dr C Ceuterick-de
Groote, University Hospital Antwerp).
The family history revealed two similar

cases (figure). There was no known con-
sanguinity.
The monozygotic twin has an almost

identical medical history and clinical picture.
She is able to stammer a few simple words.
Her answers are sometimes slightly more
appropriate, particularly for old memories.
Her knee jerks and ankle jerks are both
unusually brisk, and the plantar responses
are extensor. One brother died at the age of
53. The medical records and relatives des-
cribed difficulties with walking from the age
of 20 (maybe earlier). During the following
decades he presented a progressive spastic
paraparesis, dysarthria, mental deterioration
and urinary and faecal incontinence; no
deficits of sensation or coordination were
demonstrated. There was dysphagia in his
last years. Death was due to pneumonia.
The pedigree suggests an autosomal reces-

sive inheritance. The neurodegenerative syn-
drome in this family seems fully comparable

to the Mast syndrome, described in 1967 in
an Ohio Amish isolate by Cross and McKu-
sick.`'- There appears to be no similar cases
that have been described outside the Amish
population.

MARC D'HOOGHE
Department of Neurology,

Algemeen Ziekenhuis St J7an,
Ruddershove 10,

8000 Brugge, Belgium

1 Cross HE, McKusickVA. The mast syndrome: a
recessively inherited form of presenile de-
mentia with motor disturbances. Arch Neurol
(Chic) 1967;16:1-13.

2 Harding AE. Classification of hereditary ataxias
and paraplegias. Lancet 1983;i: 1 151-55.

3 McKusick VA. Mendelian inheritance in man.
Baltimore: The Johns Hopkins University
Press, 1990:1095.

Ultrasensitive TSH assay and anti-Par-
kinsonian treatment with levodopa

We have recently reported the association of
Parkinson's disease and hyperthyroidism in a
group of 10 patients.' In that report, symp-
toms of Parkinson's disease were always
significantly exacerbated by the development
of hyperthyroidism and improved by its
successful treatment.' We proposed that
hyperthyroidism should be suspected in all
Parkinsonian patients when their condition
deteriorates.' Since clinical diagnosis of thy-
rotoxicosis is difficult in Parkinsonian
patients, they should have a comprehensive
thyroid examination and, if there is the
slightest suspicion of hyperthyroidism, a hor-
monal evaluation of thyroid function (free T4,
ultrasensitive TSH).
Thyroid hormone levels (T3 and T4) have

been found to be normal in Parkinsonian
patients untreated or treated with levodopa.2
However, a decreased response of thyro-
tropin (TSH) after stimulation by TRH
(thyrotropin releasing hormone) has been
reported in Parkinsonian patients treated
with levadopa.3 Such a decreased TSH
response after TRH stimulation is observed
during hyperthyroidism, and is sometimes
the only hormonal abnormality, especially in
elderly patients with autonomous thyroid
nodules. Thus the decreased TSH response
after TRH-stimulation in patients treated
with levodopa could be responsible for a false
diagnosis of hyperthyroidism. These results,
however, were obtained before the ultra-
sensitive TSH determination with a mono-
clonal antibody assay was available. A low
ultrasensitive TSH level has the same sig-
nificance as a decreased TSH response to
TRH, indicating an increased negative feed-

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