The chest x ray is indicated because it may help in the diagnosis of
mononeuritis multiplex (sarcoid, Wegeners etc) but primarily, as you say,
because the sixth nerve is the "tumour nerve" and lung cancer is by far the
most likely tumour. Small cell lung cancer can very easily be metastatic
before causing PULMONARY symptoms. She already has symptoms consistent with
cancer (headache, diplopia). A CXR is usually more easily obtained than a
contrast-enhanced CT brain or an MRI, which I would regard as wasteful of
scarce resources if you haven't done a CXR.
Mark Slade
General and Chest Physician (and specialist in lung cancer)
-----Original Message-----
From: John Ryan [mailto:[log in to unmask]]
Sent: 11 October 2001 22:39
To: [log in to unmask]
Subject: Re: Isolated 6th nerve palsy
CXR ? Not done. Granted she is a smoker but she has no pulmonary sympotoms
or signs. Is a CXR really the test most likely to indicate where to go from
here ? I see junior doctors do that sort of thing all the time and I cant
help wondering if they are procrastinating and sending people for tests
because they dont know whats wrong and hoping that when the results come
back they wil have gone off duty and it will be up to someone else to sort
out a management plan.
I thought about a CT but felt that whatever the problem was, given the
isolation of her signs, that it would be most likely quite isolated and
maybe even small. Then I wondered about the need for investigation, was it
routine, urgent or emergent ? I was concerned that given the headaches
there migth be a vascular explanation for her symptoms and signs and did'nt
fancy hearing about 'this woman who went home yesterday'. Also the anatomy
throws up lots of potential nasty causes: The VIth nerve emanates from
nucelei in the dorsal pons and courses through the brainstem to exit
ventrally at the pontomedullary junction before ascending along the dorsal
aspect of teh clivus to enter the cavernous sinus where it lies close to the
carotid artery. The nerve enters the orbit through the superior orbital
fissure to innervate the lateral rectus muscle. The nerve can be affected
anywhere along its course on the brainstem, subarachnoid space, cavernous
sinus or orbit. It is often thought of as the 'tumour' nerve. It can be
affected by raised intracranial pressure or by direct compression due to
mass lesions. It can also be affected by ischaemia of a microvascular
nature in which case they often improve over 3 months. .
So I bottled out and requested a MRI on the basis that this was the test
most likely to give me a localised explanation if one existed.
But, hey the MRI was normal. Good for her. So I still dont know what the
cause is. One of my colleagues remarked how his wife had developed
bilateral VI nerve palsies and the diagnosis was an acute myasthenic episode
which responded to tensilon. And unilateral lateral rectus palsy as an
isolated presentation of Myasthenia was described last month:
Am J Emerg Med 2001 Sep;19(5):410-2 Myasthenia gravis presenting as a
unilateral abducens nerve palsy.
Maybe...
Some other causes decirbed in teh last 2 years include:
Isolated sixth nerve palsy from pontine infarct Acta Neurol Belg 2000
Dec;100(4):246-7
and
Isolated abducens nerve palsy caused by the compression of the basilar
artery: a case report Ohhashi G, Irie K, Tani S, Ogawa T, Abe T, Hata Y.:
No To Shinkei 2001 Jan;53(1):69-72
and
Sixth nerve palsy as a presenting sign of intracranial plasmacytoma and
multiple myeloma. Movsas TZ, Balcer LJ, Eggenberger ER, Hess JL, Galetta
SL.J Neuroophthalmol 2000 Dec;20(4):242-5
and of course
Isolated sixth nerve palsy: an uncommon presenting sign of multiple
sclerosis. J Neurol 2000 Sep;247(9):701-4 Barr D, Kupersmith MJ, Turbin R,
Bose S, Roth R.
and perhaps scarily:
Painless abducens palsy disclosed by spontaneous dissection of the
intracavernous internal carotid artery Ducrocq X, Lacour J, Anxionnat R,
Marchal C, Bracard S, Vespignani H.Rev Neurol (Paris) 2000 May;156(5):520-2
After her long day on the road she just wanted to go home and she has
deceided to see a neurologist of her choice privately. I have asked her to
let me know and I will feed back if I hear. I wonder how long it would have
taken him to get the MRI....
John
Dr John Ryan
----- Original Message -----
From: John Ryan <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, October 09, 2001 10:22
Subject: Isolated 6th nerve palsy
> A 48 year old, cigarette smoking, otherwise well, lady presents with a 3
day
> history of diplopia which was preceded by unilateral headache for 2 days,
> resolving with onet of diplopia. Examination reveals a marked lateral
> rectus palsy on the right side and she has already patched the eye to
> prevent diplopia. Examination is otherwise completely normal. Blood
sugar
> and BP normal, nothing to suggest demyelination or auto immune pathology.
>
> Would you ?
>
> 1) Arrange urgent CT
> 2) Arrange urgent MRI
> 3) Referr to neurology OPD, (next available appointment in a future era)
> 4) Discharge her telling her many of these resolve after 3 months (as per
> Tintanelli !)
> 5) Some other bright idea ?
>
> John Ryan
>
>
>
>
>
>
>
> Dr John Ryan
>
>
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