Friday, 14 October 2016

Anterior choroidal artery syndrome

We saw a 68-year old lady on the ward. She had no past medical history of note.
She presented to hospital with a self-terminating generalised tonic-clonic (GTCS) and in addition was found to have a dense right hemiplegia and expressive dysphasia. The presentation was preceded by a 3-4 week history of increasing confusion and disorientation.

On examination she appeared alert but had significant expressive dysphasia
She was consistently following instructions: 2 and 3 stage commands. There was a subtle ptosis on the left and unequal pupil size. No papilloedema. (Horner’s)
There was a small recent Neurosurgical scar in the right frontal region and a dense right hemiplegia. On further inspection there was wasting of FDIO on the right as well as heberden’s nodes & mild ulnar deviation of the digits. On palpation there was arthralgia in small muscles of the hands, ankle and knee on the right (- ?OA ?RA)
Auscultation of the heart was normal (with normal echocardiogram) and there were no other systemic features (no fever, lymphadenopathy or rash)

Differentials based on clinical findings:
Most likely differential is a vasculitic syndrome leading to ischaemia in the territory of anterior choroidal artery, MCA or internal carotid artery. VZV vasculitis is in the differential as is primary CNS angiitis
Angiocentric lymphoma
Vasculitis secondary to systemic disease such as rheumatoid arthritis
PML could cause this but is usually more indolent
Susacs unlikely as there is no history of headache or hearing deficit
PML would typically follow a more indolent course

Learning points highlighted in discussion of the case:

1. Differentials for confusion/delirium:
-       Drugs
-       Dementia (DLB)
-       Infection (urine and chest most commonly)
-       Head trauma (look for rhinorrhoea, evidence of previous neurosurgery, evidence
-       Hypoxia (ABG)
-       Psychiatric
-       Seizures (non-convulsive, may be secondary to either frontal or temporal seizures. Typically confusion would be fluctuant)
-       Space occupying lesion (papilloedema)
-       Metabolic (Renal failure, Liver failure, electrolyte abnormality)

2. The pathway of the internal carotid artery:
Enters the cranium through the Foramen lacerum, then travels through the
Cavernous sinus. It then turns to travel under the anterior clinoid process emerging just below and posterior to the optic canal. The internal carotid artery finally emerges through the dura just beneath the optic nerve.
There are 5 terminal branches: MCA, ACA, ophthalmic, posterior communicating and anterior choroidal artery. The ophthalmic artery supplies the contents of the orbit and continues forward to supply the central part of the forehead.

3. Syndromes related to anterior choroidal artery infarction
Most commonly patients present with a lacunar syndrome (85%) but there are case studies of confusion and aphasia, presumably where the superficial territory is involved, leading to cortical deficits.

Further reading: Palomeras E, Fossas P, Cano AT, Sanz P, Floriach M. Anterior choroidal artery infarction: a clinical, etiologic and prognostic study. Acta Neurol Scand 2008: 118: 42–47

4. Horner syndrome
Classically the patient will have ptosis, miosis and anhidrosis. There may be mild enophthalmos secondary to lid sagging. There is also increased amplitude of accommodation. Acute features of sympathetic disruption include ipsilateral conjunctival injection and nasal stuffiness.

The precise clinical manifestation depends upon the site of the lesion along the three-neuron sympathetic (adrenergic) pathway, that originates in the hypothalamus:

-       1st order neuron: descends caudally from hypothalamus to the first synapse located in the spinal cord (levels C8-T2). Causes include stroke, demyelination, pituitary or base of skull tumours, basal meningitis, neck trauma, syringomyelia, Arnold chiari malformation and spinal cord tumours.

-       2nd order neuron: travels from sympathetic trunk, through the brachial plexus, over the lung apex and ascends to the superior ganglion, located near the angle of the mandible and bifurcation of the common carotid artery. Causes include apical lung tumours (eg. Pancoast’s), lymphadenopathy (lymphoma, leukaemia, TB), lower brachial plexus trauma, common carotid or subclavian aneurysm, neuroblastoma or mandibular dental abscess.

-       3rd order neuron: ascends within the adventitia of the internal carotid artery, through the cavernous sinous in close relation to CN VI. The oculosympathetic pathway then joins V1. In the orbit the fibres innervate the iris dilator muscle as well as Muller’s muscle (responsible for a small proportion of upper lid elevation and lower lid retraction). This innervation accounts for the minor ptosis (<2mm). Anhidrosis is not a feature of 3rd order lesions as the sympathetic fibre responsible for sweating and vasodilation branch off at the superior cervical ganglion. Causes include cluster headache or migraine, herpes zoster infection, internal carotid artery dissection, carotid-cavernous fistula and temporal arteritis.

Neurological signs can help to localise the lesion:
diplopia, vertigo, ataxia, lateralised weakness à Brainstem
bilat/ipsilat weakness, long tract signs, sensory level, bladder or bowel involvement à Myelopathy
Arm pain/weakness à brachial plexus or lung apex
Ipsilateral ocular paresis & CN VI palsy, no brainstem signs à cavernous sinus
Isolated honers with neck pain àinternal carotid artery dissection

5. Neurological manifestations of rheumatoid arthritis

Manifestations may be either central or peripheral and related to the disease itself or disease modifying treatment.

CNS manifestations: cervical myelopathy (secondary to atlantoaxial subluxation), vasculitis, rheumatoid nodules within the CNS, meningitis and rarely progressive multifocal leucoencephalopathy (risk increased after rituximab therapy) and a hyperviscosity syndrome. Stroke also occurs with increased frequency

PNS manifestations: compression neuropathies (most common, secondary to joint deformities, inflamed synovium, ligaments or compressive tendon sheaths), distal sensory neuropathy, sensori-motor neuropathy or autonomic neuropathy (thought to be secondary to vasculitic process)

Neuromuscular manifestations: myopathy, disuse atrophy, denervation atrophy, myositis.

RA may rarely be complicated by secondary amyloidosis.

Drugs effects:
Nonsteroidal antiinflammatory drugs (NSAIDs) à headaches, drowsiness, and aseptic meningitis
Glucocorticoids à myopathy, depression, psychosis & intracranial hypertension
Gold à peripheral neuropathy, cranial nerve palsies and Guillain-Barré syndr
Methotrexate, Sulfasalazine and leflunomide à headaches.
Leflunomide àperipheral neuropathy
anti-TNF therapies à increase the risk of demyelinating disease

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